https://exercises.lol/videos2026-09-05 https://exercises.lol/videos/a_level_biology2026-09-05 https://exercises.lol/videos/a_level_business2026-09-05 https://exercises.lol/videos/a_level_chemistry2026-09-05 https://exercises.lol/videos/a_level_computer_science2026-09-05 https://exercises.lol/videos/a_level_economics2026-09-05 https://exercises.lol/videos/a_level_further_mathematics2026-09-05 https://exercises.lol/videos/a_level_mathematics2026-09-05 https://exercises.lol/videos/a_level_physics2026-09-05 https://exercises.lol/videos/ap_art_2d2026-09-05 https://exercises.lol/videos/ap_biology2026-09-05 https://exercises.lol/videos/ap_calculus_ab2026-09-05 https://exercises.lol/videos/ap_calculus_bc2026-09-05 https://exercises.lol/videos/ap_chemistry2026-09-05 https://exercises.lol/videos/ap_computer_science_a2026-09-05 https://exercises.lol/videos/ap_computer_science_principles2026-09-05 https://exercises.lol/videos/ap_cybersecurity2026-09-05 https://exercises.lol/videos/ap_drawing2026-09-05 https://exercises.lol/videos/ap_english_language2026-09-05 https://exercises.lol/videos/ap_english_literature2026-09-05 https://exercises.lol/videos/ap_environmental_science2026-09-05 https://exercises.lol/videos/ap_european_history2026-09-05 https://exercises.lol/videos/ap_human_geography2026-09-05 https://exercises.lol/videos/ap_macroeconomics2026-09-05 https://exercises.lol/videos/ap_microeconomics2026-09-05 https://exercises.lol/videos/ap_physics_12026-09-05 https://exercises.lol/videos/ap_physics_22026-09-05 https://exercises.lol/videos/ap_physics_c_em2026-09-05 https://exercises.lol/videos/ap_physics_c_mech2026-09-05 https://exercises.lol/videos/ap_precalculus2026-09-05 https://exercises.lol/videos/ap_psychology2026-09-05 https://exercises.lol/videos/ap_statistics2026-09-05 https://exercises.lol/videos/ap_us_history2026-09-05 https://exercises.lol/videos/ap_world_history2026-09-05 https://exercises.lol/videos/code_a_level_cs2026-09-05 https://exercises.lol/videos/code_ap_csa2026-09-05 https://exercises.lol/videos/code_ap_csp2026-09-05 https://exercises.lol/videos/code_c_basics2026-09-05 https://exercises.lol/videos/code_cyber_security2026-09-05 https://exercises.lol/videos/code_igcse_cs2026-09-05 https://exercises.lol/videos/code_javascript2026-09-05 https://exercises.lol/videos/code_latex2026-09-05 https://exercises.lol/videos/code_linux2026-09-05 https://exercises.lol/videos/code_pseudocode2026-09-05 https://exercises.lol/videos/code_python_basics2026-09-05 https://exercises.lol/videos/code_sql_databases2026-09-05 https://exercises.lol/videos/code_web_basics2026-09-05 https://exercises.lol/videos/igcse_biology2026-09-05 https://exercises.lol/videos/igcse_business_studies2026-09-03 https://exercises.lol/videos/igcse_chemistry2026-09-05 https://exercises.lol/videos/igcse_computer_science2026-09-05 https://exercises.lol/videos/igcse_economics2026-09-05 https://exercises.lol/videos/igcse_mathematics2026-09-05 https://exercises.lol/videos/igcse_physics2026-09-05 https://exercises.lol/videos/a_level_biology/cells2026-09-05https://exercises.lol/video-media/a_level_biology/cells/cells.thumb.jpg?v=1788586646How We Study CellsYou are built from about thirty trillion cells, yet you have never seen a single one. Cells are simply too small for the eye. A grain of sand is about a…https://exercises.lol/video-media/a_level_biology/cells/cells.enzh.mp4?v=17885866469852026-08-15yes https://exercises.lol/videos/a_level_biology/biological-molecules2026-09-05https://exercises.lol/video-media/a_level_biology/biological-molecules/biological-molecules.thumb.jpg?v=1788577824Biological MoleculesSuppose you have an unknown food sample. How do you tell what it is made of? Biology has a beautiful trick: add the right chemical, and the colour tells you…https://exercises.lol/video-media/a_level_biology/biological-molecules/biological-molecules.enzh.mp4?v=178857782411722026-08-15yes https://exercises.lol/videos/a_level_biology/enzymes2026-09-05https://exercises.lol/video-media/a_level_biology/enzymes/enzymes.thumb.jpg?v=1788586178EnzymesInside every cell, thousands of chemical reactions happen every second — far faster than they ever could on their own. The secret is a special kind of protein…https://exercises.lol/video-media/a_level_biology/enzymes/enzymes.enzh.mp4?v=17885861788312026-08-15yes https://exercises.lol/videos/a_level_biology/cell-membranes2026-09-05https://exercises.lol/video-media/a_level_biology/cell-membranes/cell-membranes.thumb.jpg?v=1788575944Cell MembranesEvery cell must keep the right things in and the wrong things out. That job falls to a single, astonishingly thin layer — the cell surface membrane, just two…https://exercises.lol/video-media/a_level_biology/cell-membranes/cell-membranes.enzh.mp4?v=17885759448432026-08-15yes https://exercises.lol/videos/a_level_biology/mitosis2026-09-05https://exercises.lol/video-media/a_level_biology/mitosis/mitosis.thumb.jpg?v=1788585969MitosisRight now, inside you, millions of cells are dividing. A cell grows, copies everything it contains, and splits into two — and the two daughter cells are not…https://exercises.lol/video-media/a_level_biology/mitosis/mitosis.enzh.mp4?v=17885859694392026-08-15yes https://exercises.lol/videos/a_level_biology/dna-protein-synthesis2026-09-05https://exercises.lol/video-media/a_level_biology/dna-protein-synthesis/dna-protein-synthesis.thumb.jpg?v=1788574722DNA & Protein SynthesisInside almost every one of your cells sits a molecule about two metres long, folded up so tightly you cannot see it. It is DNA, and it is written in an…https://exercises.lol/video-media/a_level_biology/dna-protein-synthesis/dna-protein-synthesis.enzh.mp4?v=17885747225732026-08-15yes https://exercises.lol/videos/a_level_biology/transport-in-plants2026-09-05https://exercises.lol/video-media/a_level_biology/transport-in-plants/transport-in-plants.thumb.jpg?v=1788588548Transport in PlantsA giant redwood lifts water more than a hundred metres into the air, every single day — and it has no heart, no muscle, no pump of any kind. So what does the…https://exercises.lol/video-media/a_level_biology/transport-in-plants/transport-in-plants.enzh.mp4?v=17885885485162026-08-15yes https://exercises.lol/videos/a_level_biology/circulatory-system2026-09-05https://exercises.lol/video-media/a_level_biology/circulatory-system/circulatory-system.thumb.jpg?v=1788577026The Circulatory SystemYour heart beats about a hundred thousand times a day, and it never gets a day off. But here is the clever part. It is not one loop. It is two. Blood leaves…https://exercises.lol/video-media/a_level_biology/circulatory-system/circulatory-system.enzh.mp4?v=17885770265562026-08-15yes https://exercises.lol/videos/a_level_biology/gas-exchange2026-09-05https://exercises.lol/video-media/a_level_biology/gas-exchange/gas-exchange.thumb.jpg?v=1788587749The Gas Exchange SystemSpread the inside of your lungs out flat and it would cover about seventy square metres — roughly half a tennis court. That whole area is folded up inside your…https://exercises.lol/video-media/a_level_biology/gas-exchange/gas-exchange.enzh.mp4?v=17885877494182026-08-15yes https://exercises.lol/videos/a_level_biology/infectious-disease2026-09-05https://exercises.lol/video-media/a_level_biology/infectious-disease/infectious-disease.thumb.jpg?v=1788577377Infectious DiseaseThe animal that kills the most people every year is not the shark or the snake. It is the mosquito. And the strange thing is that the mosquito itself does…https://exercises.lol/video-media/a_level_biology/infectious-disease/infectious-disease.enzh.mp4?v=17885773775082026-08-15yes https://exercises.lol/videos/a_level_biology/immunity2026-09-05https://exercises.lol/video-media/a_level_biology/immunity/immunity.thumb.jpg?v=1788585454ImmunityCatch measles once and you will almost certainly never catch it again. Your body has not become tougher, and the virus has not become weaker. What has changed…https://exercises.lol/video-media/a_level_biology/immunity/immunity.enzh.mp4?v=17885854545172026-08-15yes https://exercises.lol/videos/a_level_biology/respiration2026-09-05https://exercises.lol/video-media/a_level_biology/respiration/respiration.thumb.jpg?v=1788586397RespirationAt any moment your body holds only about fifty grams of ATP. Yet over a single day you will make and spend roughly your own body weight of it. The same…https://exercises.lol/video-media/a_level_biology/respiration/respiration.enzh.mp4?v=17885863975882026-08-15yes https://exercises.lol/videos/a_level_biology/photosynthesis2026-09-05https://exercises.lol/video-media/a_level_biology/photosynthesis/photosynthesis.thumb.jpg?v=1788587472PhotosynthesisHere is something strange about a tree. Almost none of it came out of the ground. The wood, the leaves, the fruit — nearly all of that mass was pulled out of…https://exercises.lol/video-media/a_level_biology/photosynthesis/photosynthesis.enzh.mp4?v=17885874725382026-08-15yes https://exercises.lol/videos/a_level_biology/homeostasis2026-09-05https://exercises.lol/video-media/a_level_biology/homeostasis/homeostasis.thumb.jpg?v=1788577255HomeostasisLook at a day's worth of blood sugar. Three big meals go in — and the level hardly stirs. It wanders a little, then comes straight back. That is not luck, and…https://exercises.lol/video-media/a_level_biology/homeostasis/homeostasis.enzh.mp4?v=17885772555812026-08-15yes https://exercises.lol/videos/a_level_biology/nerves-and-muscles2026-09-05https://exercises.lol/video-media/a_level_biology/nerves-and-muscles/nerves-and-muscles.thumb.jpg?v=1788577602Nerves and MusclesTouch something hot and your hand is already moving before you feel the pain. The signal never went to your brain to ask permission. It ran into the spinal…https://exercises.lol/video-media/a_level_biology/nerves-and-muscles/nerves-and-muscles.enzh.mp4?v=17885776025782026-08-15yes https://exercises.lol/videos/a_level_biology/genetics2026-09-05https://exercises.lol/video-media/a_level_biology/genetics/genetics.thumb.jpg?v=1788590781GeneticsYou have twenty three pairs of chromosomes. When a gamete is made, each pair lines up independently — either way round — so the number of different gametes you…https://exercises.lol/video-media/a_level_biology/genetics/genetics.enzh.mp4?v=17885907815752026-08-15yes https://exercises.lol/videos/a_level_biology/variation-and-evolution2026-09-05https://exercises.lol/video-media/a_level_biology/variation-and-evolution/variation-and-evolution.thumb.jpg?v=1788585668Variation and EvolutionIn the early eighteen hundreds, almost every peppered moth in England was pale and speckled, which hid it beautifully on lichen-covered bark. Then the…https://exercises.lol/video-media/a_level_biology/variation-and-evolution/variation-and-evolution.enzh.mp4?v=17885856685022026-08-15yes https://exercises.lol/videos/a_level_biology/biodiversity2026-09-05https://exercises.lol/video-media/a_level_biology/biodiversity/biodiversity.thumb.jpg?v=1788577082BiodiversityAbout one point seven million species have been described and given a name. The best estimates say there are probably eight to ten million out there. So most…https://exercises.lol/video-media/a_level_biology/biodiversity/biodiversity.enzh.mp4?v=17885770824782026-08-15yes https://exercises.lol/videos/a_level_biology/genetic-technology2026-09-05https://exercises.lol/video-media/a_level_biology/genetic-technology/genetic-technology.thumb.jpg?v=1788579266Genetic technologyTwo cotton plants. Same field, same insects, same week. The one on the left is barely touched. The one on the right has been eaten to bare stalks. The…https://exercises.lol/video-media/a_level_biology/genetic-technology/genetic-technology.enzh.mp4?v=17885792665102026-08-15yes https://exercises.lol/videos/a_level_business/business-basics2026-09-05https://exercises.lol/video-media/a_level_business/business-basics/business-basics.thumb.jpg?v=1788592368Business and its EnvironmentLook at a cup of coffee. The beans inside it cost a few cents. The milk, the cup, the lid — a few cents more. Yet people happily pay three dollars for it. So…https://exercises.lol/video-media/a_level_business/business-basics/business-basics.enzh.mp4?v=178859236813032026-08-15yes https://exercises.lol/videos/a_level_business/human-resources2026-09-05https://exercises.lol/video-media/a_level_business/human-resources/human-resources.thumb.jpg?v=1788574443Human Resource ManagementTwo factories. Same machines, same materials, same hours. One makes twice as much as the other. The difference is not the equipment — it is the people. Labour…https://exercises.lol/video-media/a_level_business/human-resources/human-resources.enzh.mp4?v=17885744436242026-08-15yes https://exercises.lol/videos/a_level_business/marketing2026-09-05https://exercises.lol/video-media/a_level_business/marketing/marketing.thumb.jpg?v=1788591973MarketingTwo shops sell the same coffee at the same price. One is always busy; the other sits empty. Nothing about the product explains it. The difference is marketing…https://exercises.lol/video-media/a_level_business/marketing/marketing.enzh.mp4?v=17885919739142026-08-15yes https://exercises.lol/videos/a_level_business/operations2026-09-05https://exercises.lol/video-media/a_level_business/operations/operations.thumb.jpg?v=1788601632Operations ManagementA car factory takes in steel, plastic, glass, electricity and hours of work. Out the other end comes a car worth far more than everything that went into it.…https://exercises.lol/video-media/a_level_business/operations/operations.enzh.mp4?v=17886016324862026-08-15yes https://exercises.lol/videos/a_level_business/finance2026-09-05https://exercises.lol/video-media/a_level_business/finance/finance.thumb.jpg?v=1788587476Finance and AccountingA business can be profitable and still die. Here is how. You sell a hundred thousand pounds of goods on credit in March. The profit looks excellent. But the…https://exercises.lol/video-media/a_level_business/finance/finance.enzh.mp4?v=17885874769502026-08-15yes https://exercises.lol/videos/a_level_business/external-influences2026-09-05https://exercises.lol/video-media/a_level_business/external-influences/external-influences.thumb.jpg?v=1788573541External Influences and StrategyIn two thousand and eight, thousands of well-run firms went under. Their products were good. Their staff were good. Their costs were under control. What killed…https://exercises.lol/video-media/a_level_business/external-influences/external-influences.enzh.mp4?v=17885735414892026-08-15yes https://exercises.lol/videos/a_level_business/organisation2026-09-05https://exercises.lol/video-media/a_level_business/organisation/organisation.thumb.jpg?v=1788591142Organisation, Leadership and HRMA director says: cut costs by five percent this quarter. It passes to a senior manager, then a department head, then a supervisor, then the team. By the time…https://exercises.lol/video-media/a_level_business/organisation/organisation.enzh.mp4?v=17885911425142026-08-15yes https://exercises.lol/videos/a_level_business/marketing-a-level2026-09-05https://exercises.lol/video-media/a_level_business/marketing-a-level/marketing-a-level.thumb.jpg?v=1788576660Marketing (A Level)Every shop is running on numbers. How much to order. What price to charge. Which new product to try. Get those wrong, and food goes in the bin, or the shelves…https://exercises.lol/video-media/a_level_business/marketing-a-level/marketing-a-level.enzh.mp4?v=17885766604852026-08-15yes https://exercises.lol/videos/a_level_business/operations-management-a-level2026-09-05https://exercises.lol/video-media/a_level_business/operations-management-a-level/operations-management-a-level.thumb.jpg?v=1788575638Operations management (A Level)A company promised its new factory in a hundred and fifteen weeks. It opened thirty weeks late, at a huge cost in wages and rent. One task slipped in the…https://exercises.lol/video-media/a_level_business/operations-management-a-level/operations-management-a-level.enzh.mp4?v=17885756384652026-08-15yes https://exercises.lol/videos/a_level_business/finance-and-accounting-a-level2026-09-05https://exercises.lol/video-media/a_level_business/finance-and-accounting-a-level/finance-and-accounting-a-level.thumb.jpg?v=1788585911Finance and accounting (A Level)Two shops on the same street. Both sold five hundred thousand pounds of goods last year, and they look identical. But one is about to open three new branches…https://exercises.lol/video-media/a_level_business/finance-and-accounting-a-level/finance-and-accounting-a-level.enzh.mp4?v=17885859115752026-08-15yes https://exercises.lol/videos/a_level_chemistry/atomic-structure2026-09-05https://exercises.lol/video-media/a_level_chemistry/atomic-structure/atomic-structure.thumb.jpg?v=1788574736Atomic StructureNo one has ever seen inside an atom. It is far too small — a single atom is about a million times thinner than a human hair. And yet we know exactly how its…https://exercises.lol/video-media/a_level_chemistry/atomic-structure/atomic-structure.enzh.mp4?v=178857473613852026-08-15yes https://exercises.lol/videos/a_level_chemistry/moles-stoichiometry2026-09-05https://exercises.lol/video-media/a_level_chemistry/moles-stoichiometry/moles-stoichiometry.thumb.jpg?v=1788572316Atoms, Molecules & StoichiometryHere is a problem. A single teaspoon of water holds about two hundred thousand billion billion molecules. You could never count them — not in a lifetime, not…https://exercises.lol/video-media/a_level_chemistry/moles-stoichiometry/moles-stoichiometry.enzh.mp4?v=178857231611412026-08-15yes https://exercises.lol/videos/a_level_chemistry/chemical-bonding2026-09-05https://exercises.lol/video-media/a_level_chemistry/chemical-bonding/chemical-bonding.thumb.jpg?v=1788576374Chemical BondingTwo molecules, almost the same size. Water, and hydrogen sulfide. Sulfur sits directly below oxygen in the Periodic Table, so you would expect the two to…https://exercises.lol/video-media/a_level_chemistry/chemical-bonding/chemical-bonding.enzh.mp4?v=17885763749052026-08-15yes https://exercises.lol/videos/a_level_chemistry/states-of-matter2026-09-05https://exercises.lol/video-media/a_level_chemistry/states-of-matter/states-of-matter.thumb.jpg?v=1788600379States of MatterDiamond melts at three thousand five hundred and fifty degrees Celsius. Iodine melts at one hundred and fourteen. Both are made only of non-metal atoms, and in…https://exercises.lol/video-media/a_level_chemistry/states-of-matter/states-of-matter.enzh.mp4?v=17886003794512026-08-15yes https://exercises.lol/videos/a_level_chemistry/energetics2026-09-05https://exercises.lol/video-media/a_level_chemistry/energetics/energetics.thumb.jpg?v=1788601016Chemical EnergeticsA Bunsen burner gets hot enough to soften glass. An instant cold pack, squeezed once, drops close to freezing. Both are just chemical reactions — one in a…https://exercises.lol/video-media/a_level_chemistry/energetics/energetics.enzh.mp4?v=17886010165012026-08-15yes https://exercises.lol/videos/a_level_chemistry/redox2026-09-05https://exercises.lol/video-media/a_level_chemistry/redox/redox.thumb.jpg?v=1788573205Electrochemistry & RedoxTwo pieces of iron. One is quietly rusting on a fence. The other sits inside a battery, pushing electrons through your phone. They look like completely…https://exercises.lol/video-media/a_level_chemistry/redox/redox.enzh.mp4?v=17885732053942026-08-15yes https://exercises.lol/videos/a_level_chemistry/equilibria2026-09-05https://exercises.lol/video-media/a_level_chemistry/equilibria/equilibria.thumb.jpg?v=1788575113EquilibriaSome reversible reactions never finish. You mix the reactants, the colour changes, and then everything just stops — halfway. Leave it for a week and it looks…https://exercises.lol/video-media/a_level_chemistry/equilibria/equilibria.enzh.mp4?v=17885751136122026-08-15yes https://exercises.lol/videos/a_level_chemistry/reaction-kinetics2026-09-05https://exercises.lol/video-media/a_level_chemistry/reaction-kinetics/reaction-kinetics.thumb.jpg?v=1788585019Reaction kineticsIron left outside takes years to rust away. Strike a match, and almost the same chemistry — oxygen attacking a fuel — is over in less than a second. Same…https://exercises.lol/video-media/a_level_chemistry/reaction-kinetics/reaction-kinetics.enzh.mp4?v=17885850194322026-08-15yes https://exercises.lol/videos/a_level_chemistry/chemical-periodicity2026-09-05https://exercises.lol/video-media/a_level_chemistry/chemical-periodicity/chemical-periodicity.thumb.jpg?v=1788597691The Periodic Table: chemical periodicitySodium and argon sit in the same row of the Periodic Table, with only six elements between them. Drop sodium into cold water and it melts into a shining ball…https://exercises.lol/video-media/a_level_chemistry/chemical-periodicity/chemical-periodicity.enzh.mp4?v=17885976915232026-08-15yes https://exercises.lol/videos/a_level_chemistry/group-22026-09-05https://exercises.lol/video-media/a_level_chemistry/group-2/group-2.thumb.jpg?v=1788572768Group 2Before a stomach X-ray, the patient is asked to drink a thick white liquid. It is full of barium — and barium ions are poisonous. Swallow a soluble barium salt…https://exercises.lol/video-media/a_level_chemistry/group-2/group-2.enzh.mp4?v=17885727684812026-08-15yes https://exercises.lol/videos/a_level_chemistry/group-172026-09-05https://exercises.lol/video-media/a_level_chemistry/group-17/group-17.thumb.jpg?v=1788600417Group 17Here are three colourless solutions. They look exactly the same. One is a chloride, one is a bromide, one is an iodide — but you cannot tell which is which by…https://exercises.lol/video-media/a_level_chemistry/group-17/group-17.enzh.mp4?v=17886004174472026-08-15yes https://exercises.lol/videos/a_level_chemistry/nitrogen-sulfur2026-09-05https://exercises.lol/video-media/a_level_chemistry/nitrogen-sulfur/nitrogen-sulfur.thumb.jpg?v=1788577017Nitrogen and sulfurTake a breath. Nearly four fifths of what just went into your lungs was nitrogen — and it came straight back out again, completely unchanged. Nitrogen is…https://exercises.lol/video-media/a_level_chemistry/nitrogen-sulfur/nitrogen-sulfur.enzh.mp4?v=17885770174602026-08-15yes https://exercises.lol/videos/a_level_chemistry/organic-intro2026-09-05https://exercises.lol/video-media/a_level_chemistry/organic-intro/organic-intro.thumb.jpg?v=1788576220An introduction to AS Level organic chemistryChemists have found more than ten million hydrocarbons and carbon compounds. Ten million. So how can anyone learn organic chemistry? Because almost all of them…https://exercises.lol/video-media/a_level_chemistry/organic-intro/organic-intro.enzh.mp4?v=17885762205352026-08-15yes https://exercises.lol/videos/a_level_chemistry/hydrocarbons2026-09-05https://exercises.lol/video-media/a_level_chemistry/hydrocarbons/hydrocarbons.thumb.jpg?v=1788602565HydrocarbonsTwo clear liquids, both nothing but carbon and hydrogen. And two test tubes of orange bromine water. Shake the first liquid into one tube, the second into the…https://exercises.lol/video-media/a_level_chemistry/hydrocarbons/hydrocarbons.enzh.mp4?v=17886025655932026-08-15yes https://exercises.lol/videos/a_level_chemistry/halogen-compounds2026-09-05https://exercises.lol/video-media/a_level_chemistry/halogen-compounds/halogen-compounds.thumb.jpg?v=1788575859Halogen compoundsPress the button on a can of freezer spray, and your skin goes numb with cold. Inside is a halogenoalkane: an alkane with a halogen atom in place of one…https://exercises.lol/video-media/a_level_chemistry/halogen-compounds/halogen-compounds.enzh.mp4?v=17885758594512026-08-15yes https://exercises.lol/videos/a_level_chemistry/hydroxy-compounds2026-09-05https://exercises.lol/video-media/a_level_chemistry/hydroxy-compounds/hydroxy-compounds.thumb.jpg?v=1788574103Hydroxy compoundsSqueeze hand sanitiser onto your hands. It feels cold, and then it is gone. That is ethanol — the alcohol that kills the microbes. Ethanol is only a short…https://exercises.lol/video-media/a_level_chemistry/hydroxy-compounds/hydroxy-compounds.enzh.mp4?v=17885741034992026-08-15yes https://exercises.lol/videos/a_level_chemistry/carbonyl-compounds2026-09-05https://exercises.lol/video-media/a_level_chemistry/carbonyl-compounds/carbonyl-compounds.thumb.jpg?v=1788575797Carbonyl compoundsOpen a bottle of nail polish remover, and that sharp smell is propanone. Your own body makes a little of it every day. All of that comes from one small group…https://exercises.lol/video-media/a_level_chemistry/carbonyl-compounds/carbonyl-compounds.enzh.mp4?v=17885757974822026-08-15yes https://exercises.lol/videos/a_level_chemistry/carboxylic-acids2026-09-05https://exercises.lol/video-media/a_level_chemistry/carboxylic-acids/carboxylic-acids.thumb.jpg?v=1788576361Carboxylic acids and derivativesOpen a bottle of vinegar and you know it at once. That sharp smell is ethanoic acid, and vinegar is only a weak solution of it in water. Pour a little onto…https://exercises.lol/video-media/a_level_chemistry/carboxylic-acids/carboxylic-acids.enzh.mp4?v=17885763614822026-08-15yes https://exercises.lol/videos/a_level_chemistry/nitrogen-compounds2026-09-05https://exercises.lol/video-media/a_level_chemistry/nitrogen-compounds/nitrogen-compounds.thumb.jpg?v=1788576645Nitrogen compoundsLook at the thread in a jacket, a rope, a pair of stockings: nylon. It is built from two kinds of molecule, joined again and again — one with a nitrogen group…https://exercises.lol/video-media/a_level_chemistry/nitrogen-compounds/nitrogen-compounds.enzh.mp4?v=17885766454652026-08-15yes https://exercises.lol/videos/a_level_chemistry/polymerisation2026-09-05https://exercises.lol/video-media/a_level_chemistry/polymerisation/polymerisation.thumb.jpg?v=1788575803PolymerisationLook around you. A drinks cup. A shopping bag. A plastic wrapper. All three are made of the same kind of thing: one enormous molecule, a chain that is tens of…https://exercises.lol/video-media/a_level_chemistry/polymerisation/polymerisation.enzh.mp4?v=17885758034432026-08-15yes https://exercises.lol/videos/a_level_chemistry/organic-synthesis2026-09-05https://exercises.lol/video-media/a_level_chemistry/organic-synthesis/organic-synthesis.thumb.jpg?v=1788575343Organic synthesisLook at almost any medicine. It is a complicated molecule, and it began as something simple — often a small molecule from crude oil. No single reaction turns…https://exercises.lol/video-media/a_level_chemistry/organic-synthesis/organic-synthesis.enzh.mp4?v=17885753434802026-08-15yes https://exercises.lol/videos/a_level_chemistry/analytical-techniques-as2026-09-05https://exercises.lol/video-media/a_level_chemistry/analytical-techniques-as/analytical-techniques-as.thumb.jpg?v=1788576573Analytical techniques (AS)You have just made a new compound. It is a clear liquid in a flask, with no label, and you cannot see a single molecule. How do you prove what it is? You ask…https://exercises.lol/video-media/a_level_chemistry/analytical-techniques-as/analytical-techniques-as.enzh.mp4?v=17885765735242026-08-15yes https://exercises.lol/videos/a_level_chemistry/energetics-a22026-09-05https://exercises.lol/video-media/a_level_chemistry/energetics-a2/energetics-a2.thumb.jpg?v=1788600638Chemical energetics (A2)Sodium is a soft metal that burns in air. Chlorine is a choking, poisonous gas. Put them together and you get table salt. Making one mole of it gives out a…https://exercises.lol/video-media/a_level_chemistry/energetics-a2/energetics-a2.enzh.mp4?v=17886006384822026-08-15yes https://exercises.lol/videos/a_level_chemistry/electrochemistry-a22026-09-05https://exercises.lol/video-media/a_level_chemistry/electrochemistry-a2/electrochemistry-a2.thumb.jpg?v=1788601401Electrochemistry (A2)Two things in your pocket run on the same chemistry. A battery: a reaction that wants to happen pushes electrons through a wire. And the charger: we push those…https://exercises.lol/video-media/a_level_chemistry/electrochemistry-a2/electrochemistry-a2.enzh.mp4?v=17886014014732026-08-15yes https://exercises.lol/videos/a_level_chemistry/equilibria-a22026-09-05https://exercises.lol/video-media/a_level_chemistry/equilibria-a2/equilibria-a2.thumb.jpg?v=1788574945Equilibria (A2)Your blood is held at pH seven point four. Move it a few tenths either way and you are in hospital. Yet all day, acid pours in — from your food, and from your…https://exercises.lol/video-media/a_level_chemistry/equilibria-a2/equilibria-a2.enzh.mp4?v=17885749454752026-08-15yes https://exercises.lol/videos/a_level_chemistry/kinetics-a22026-09-05https://exercises.lol/video-media/a_level_chemistry/kinetics-a2/kinetics-a2.thumb.jpg?v=1788576685Reaction kinetics (A2)Here is a real reaction: hydrogen peroxide reacting with iodide ions in acid. Look at the balanced equation. It uses two iodide ions and two hydrogen ions…https://exercises.lol/video-media/a_level_chemistry/kinetics-a2/kinetics-a2.enzh.mp4?v=17885766854802026-08-15yes https://exercises.lol/videos/a_level_chemistry/group-2-a22026-09-05https://exercises.lol/video-media/a_level_chemistry/group-2-a2/group-2-a2.thumb.jpg?v=1788576720Group 2 (A2)Here is a puzzle. Go down Group 2, from magnesium to barium, and the hydroxides get more soluble. Go down the same group, and the sulfates get less soluble.…https://exercises.lol/video-media/a_level_chemistry/group-2-a2/group-2-a2.enzh.mp4?v=17885767204862026-08-15yes https://exercises.lol/videos/a_level_chemistry/transition-elements2026-09-05https://exercises.lol/video-media/a_level_chemistry/transition-elements/transition-elements.thumb.jpg?v=1788575503Chemistry of transition elementsLook at these six test tubes: pink, orange, yellow, green, blue, violet. Every one holds a d-block metal in water, and every metal comes from the same short…https://exercises.lol/video-media/a_level_chemistry/transition-elements/transition-elements.enzh.mp4?v=17885755035042026-08-15yes https://exercises.lol/videos/a_level_chemistry/organic-intro-a22026-09-05https://exercises.lol/video-media/a_level_chemistry/organic-intro-a2/organic-intro-a2.thumb.jpg?v=1788575995An introduction to A Level organic chemistryTwo molecules. Same atoms, same bonds. The only difference: one is the mirror image of the other, like your left hand and your right hand. And yet one of them…https://exercises.lol/video-media/a_level_chemistry/organic-intro-a2/organic-intro-a2.enzh.mp4?v=17885759955082026-08-15yes https://exercises.lol/videos/a_level_chemistry/arenes2026-09-05https://exercises.lol/video-media/a_level_chemistry/arenes/arenes.thumb.jpg?v=1788576404Hydrocarbons (A2): arenesOrange bromine water is the classic test for a double bond. Shake it with an alkene, and the orange colour vanishes at once. Now shake the very same bromine…https://exercises.lol/video-media/a_level_chemistry/arenes/arenes.enzh.mp4?v=17885764044622026-08-15yes https://exercises.lol/videos/a_level_chemistry/halogen-a22026-09-05https://exercises.lol/video-media/a_level_chemistry/halogen-a2/halogen-a2.thumb.jpg?v=1788575490Halogen compounds (A2)A farmer sprays a field. Many of the pesticides and weedkillers in that tank are halogenoarenes: a chlorine atom bonded straight onto a benzene ring. Now look…https://exercises.lol/video-media/a_level_chemistry/halogen-a2/halogen-a2.enzh.mp4?v=17885754904762026-08-15yes https://exercises.lol/videos/a_level_chemistry/phenol2026-09-05https://exercises.lol/video-media/a_level_chemistry/phenol/phenol.thumb.jpg?v=1788575870Hydroxy compounds (A2): phenolIn the eighteen sixties, surgery was terrifying. The cutting could be survived; the infection that followed often could not. After an amputation, almost half…https://exercises.lol/video-media/a_level_chemistry/phenol/phenol.enzh.mp4?v=17885758705182026-08-15yes https://exercises.lol/videos/a_level_chemistry/carboxylic-a22026-09-05https://exercises.lol/video-media/a_level_chemistry/carboxylic-a2/carboxylic-a2.thumb.jpg?v=1788575498Carboxylic acids and derivatives (A2)Open a medicine cabinet and pick up a packet of aspirin. That tablet is an ester. At AS you met one small group: the carboxyl group. At A2 it becomes three new…https://exercises.lol/video-media/a_level_chemistry/carboxylic-a2/carboxylic-a2.enzh.mp4?v=17885754984872026-08-15yes https://exercises.lol/videos/a_level_chemistry/nitrogen-organic2026-09-05https://exercises.lol/video-media/a_level_chemistry/nitrogen-organic/nitrogen-organic.thumb.jpg?v=1788601305Nitrogen compoundsLook at three very different things. A sweet, dyed bright orange. A painkiller tablet. And the protein in your muscles. They share almost nothing — except one…https://exercises.lol/video-media/a_level_chemistry/nitrogen-organic/nitrogen-organic.enzh.mp4?v=17886013054692026-08-15yes https://exercises.lol/videos/a_level_chemistry/polymerisation-a22026-09-05https://exercises.lol/video-media/a_level_chemistry/polymerisation-a2/polymerisation-a2.thumb.jpg?v=1788601128Polymerisation (A2)Look at three very different things. A nylon rope. A plastic drinks bottle. The protein in your own hair. They seem to have nothing in common. Yet all three…https://exercises.lol/video-media/a_level_chemistry/polymerisation-a2/polymerisation-a2.enzh.mp4?v=17886011284782026-08-15yes https://exercises.lol/videos/a_level_chemistry/synthesis-a22026-09-05https://exercises.lol/video-media/a_level_chemistry/synthesis-a2/synthesis-a2.thumb.jpg?v=1788577351Organic synthesis (A2)Three very different things: a bright orange dye, a painkiller, and a tough plastic. All three begin as the same colourless liquid — benzene. But no single…https://exercises.lol/video-media/a_level_chemistry/synthesis-a2/synthesis-a2.enzh.mp4?v=17885773514722026-08-15yes https://exercises.lol/videos/a_level_chemistry/nmr-spectroscopy2026-09-05https://exercises.lol/video-media/a_level_chemistry/nmr-spectroscopy/nmr-spectroscopy.thumb.jpg?v=1788600744Analytical techniques (A2): NMRHere are seven different molecules. Every one has five carbons, ten hydrogens and one oxygen, and every one contains a carbonyl group. Weigh them in a mass…https://exercises.lol/video-media/a_level_chemistry/nmr-spectroscopy/nmr-spectroscopy.enzh.mp4?v=17886007444862026-08-15yes https://exercises.lol/videos/a_level_computer_science/databases2026-09-05https://exercises.lol/video-media/a_level_computer_science/databases/databases.thumb.jpg?v=1788597186Databases & the Relational ModelBefore databases, each program kept its own flat files — one file per program. Picture a shop. The sales program, the billing program, and the shipping program…https://exercises.lol/video-media/a_level_computer_science/databases/databases.enzh.mp4?v=178859718610362026-08-15yes https://exercises.lol/videos/a_level_computer_science/user-defined-types2026-09-05https://exercises.lol/video-media/a_level_computer_science/user-defined-types/user-defined-types.thumb.jpg?v=1788580265User-Defined Data TypesA plain string field will happily store nonsense. Ask for a vehicle type, and someone types Bananas — the program accepts it without a murmur. But if you…https://exercises.lol/video-media/a_level_computer_science/user-defined-types/user-defined-types.enzh.mp4?v=17885802659142026-08-15yes https://exercises.lol/videos/a_level_computer_science/protocols2026-09-05https://exercises.lol/video-media/a_level_computer_science/protocols/protocols.thumb.jpg?v=1788581039Why Protocols Are NeededTwo computers want to talk, but one sends its data one way and the other expects it completely differently. The result is gibberish — like two people speaking…https://exercises.lol/video-media/a_level_computer_science/protocols/protocols.enzh.mp4?v=17885810396772026-08-15yes https://exercises.lol/videos/a_level_computer_science/risc-cisc2026-09-05https://exercises.lol/video-media/a_level_computer_science/risc-cisc/risc-cisc.thumb.jpg?v=1788580236RISC, Pipelines & LogicTwo chip designers face the same problem: make programs run fast. One says — build powerful instructions, so each one does a lot of work. The other says — keep…https://exercises.lol/video-media/a_level_computer_science/risc-cisc/risc-cisc.enzh.mp4?v=17885802369022026-08-15yes https://exercises.lol/videos/a_level_computer_science/os-resources2026-09-05https://exercises.lol/video-media/a_level_computer_science/os-resources/os-resources.thumb.jpg?v=1788586013Resources, Compilers & RPNOpen a browser, a music player, and a game. You have one processor — maybe a few cores — yet all of them seem to run at once. And together they want more…https://exercises.lol/video-media/a_level_computer_science/os-resources/os-resources.enzh.mp4?v=17885860138442026-08-15yes https://exercises.lol/videos/a_level_computer_science/encryption2026-09-05https://exercises.lol/video-media/a_level_computer_science/encryption/encryption.thumb.jpg?v=1788597094How Encryption WorksLook at the padlock in your browser's address bar. You typed your bank's name, and somehow your laptop is now certain it is really talking to the bank — and…https://exercises.lol/video-media/a_level_computer_science/encryption/encryption.enzh.mp4?v=17885970947992026-08-15yes https://exercises.lol/videos/a_level_computer_science/artificial-intelligence2026-09-05https://exercises.lol/video-media/a_level_computer_science/artificial-intelligence/artificial-intelligence.thumb.jpg?v=1788597051What AI IsNobody ever wrote the rules for telling a cat from a dog. No programmer sat down and typed "if it has pointed ears and whiskers". And yet your phone does it…https://exercises.lol/video-media/a_level_computer_science/artificial-intelligence/artificial-intelligence.enzh.mp4?v=17885970517912026-08-15yes https://exercises.lol/videos/a_level_computer_science/searching-sorting2026-09-05https://exercises.lol/video-media/a_level_computer_science/searching-sorting/searching-sorting.thumb.jpg?v=1788599541Searching & SortingA phone book with a million names. If you check them one at a time, you might make a million comparisons. But you already know the trick: open it in the…https://exercises.lol/video-media/a_level_computer_science/searching-sorting/searching-sorting.enzh.mp4?v=17885995419322026-08-15yes https://exercises.lol/videos/a_level_computer_science/paradigms2026-09-05https://exercises.lol/video-media/a_level_computer_science/paradigms/paradigms.thumb.jpg?v=1788590078Programming ParadigmsHere is one job: list every student with an A grade. One programmer writes a loop — start at the first record, check the grade, add the name to a list, move…https://exercises.lol/video-media/a_level_computer_science/paradigms/paradigms.enzh.mp4?v=17885900788282026-08-15yes https://exercises.lol/videos/a_level_economics/basic-economic-ideas2026-09-05https://exercises.lol/video-media/a_level_economics/basic-economic-ideas/basic-economic-ideas.thumb.jpg?v=1788578623Basic Economic IdeasWrite down everything you want. A phone, a bigger home, travel, a good education. The list never ends. Now look at what the world has: a fixed amount of land…https://exercises.lol/video-media/a_level_economics/basic-economic-ideas/basic-economic-ideas.enzh.mp4?v=178857862311182026-08-15yes https://exercises.lol/videos/a_level_economics/economic-problem2026-09-05https://exercises.lol/video-media/a_level_economics/economic-problem/economic-problem.thumb.jpg?v=1788578941The Fundamental Economic ProblemThink of everything you want. A better phone. More free time. Now think of what the world actually has: a fixed amount of land, a fixed number of workers, and…https://exercises.lol/video-media/a_level_economics/economic-problem/economic-problem.enzh.mp4?v=178857894112002026-08-15yes https://exercises.lol/videos/a_level_economics/price-system-and-the2026-09-05https://exercises.lol/video-media/a_level_economics/price-system-and-the/price-system-and-the.thumb.jpg?v=1788590394The price system and the microeconomyNobody in this market is in charge. No official decides what a kilo of tomatoes should cost. Yet every stall has a price, and by evening almost everything is…https://exercises.lol/video-media/a_level_economics/price-system-and-the/price-system-and-the.enzh.mp4?v=17885903949702026-08-15yes https://exercises.lol/videos/a_level_economics/government-microeconomic-intervention2026-09-05https://exercises.lol/video-media/a_level_economics/government-microeconomic-intervention/government-microeconomic-intervention.thumb.jpg?v=1788578915Government microeconomic interventionThis power station makes electricity, and you pay for the electricity. But the people living beside it breathe the smoke, and they never agreed to anything.…https://exercises.lol/video-media/a_level_economics/government-microeconomic-intervention/government-microeconomic-intervention.enzh.mp4?v=17885789158932026-08-15yes https://exercises.lol/videos/a_level_economics/macroeconomy2026-09-05https://exercises.lol/video-media/a_level_economics/macroeconomy/macroeconomy.thumb.jpg?v=1788578705The macroeconomyA city at night: every light is somebody working, building, selling. A shelf of food: every price tag changed this year. An economy is too big to see, so we…https://exercises.lol/video-media/a_level_economics/macroeconomy/macroeconomy.enzh.mp4?v=178857870510312026-08-15yes https://exercises.lol/videos/a_level_economics/government-macroeconomic-intervention2026-09-05https://exercises.lol/video-media/a_level_economics/government-macroeconomic-intervention/government-macroeconomic-intervention.thumb.jpg?v=1788579326Government macroeconomic interventionPrices are rising fast. Jobs are hard to find. Growth has stopped. Who fixes that? Two buildings decide. In one, the government chooses what to spend and what…https://exercises.lol/video-media/a_level_economics/government-macroeconomic-intervention/government-macroeconomic-intervention.enzh.mp4?v=17885793265322026-08-15yes https://exercises.lol/videos/a_level_economics/international-economic-issues2026-09-05https://exercises.lol/video-media/a_level_economics/international-economic-issues/international-economic-issues.thumb.jpg?v=1788587624International economic issuesLook at the label on your phone, your shoes, your desk lamp. Almost none of it was made in the country where you are sitting. It arrived in steel boxes, on…https://exercises.lol/video-media/a_level_economics/international-economic-issues/international-economic-issues.enzh.mp4?v=17885876245462026-08-15yes https://exercises.lol/videos/a_level_economics/price-system-and-the-microeconomy-72026-09-05https://exercises.lol/video-media/a_level_economics/price-system-and-the-microeconomy-7/price-system-and-the-microeconomy-7.thumb.jpg?v=1788578647The price system and the microeconomy (A Level)Look at these shoppers. Each has a limited budget, and every extra thing they buy gives a little less pleasure than the last. Now a huge steel plant: it makes…https://exercises.lol/video-media/a_level_economics/price-system-and-the-microeconomy-7/price-system-and-the-microeconomy-7.enzh.mp4?v=178857864711292026-08-15yes https://exercises.lol/videos/a_level_economics/government-microeconomic-intervention-a2026-09-03https://exercises.lol/video-media/a_level_economics/government-microeconomic-intervention-a/government-microeconomic-intervention-a.thumb.jpg?v=1788452482Government microeconomic intervention (A Level)Three ordinary pictures. Cigarettes, sold cheaply to anyone who wants them. A hillside of tin roofs, looking down on a rich city district. A factory floor…https://exercises.lol/video-media/a_level_economics/government-microeconomic-intervention-a/government-microeconomic-intervention-a.enzh.mp4?v=17884524824992026-08-15yes https://exercises.lol/videos/a_level_economics/macroeconomy-a-level2026-09-03https://exercises.lol/video-media/a_level_economics/macroeconomy-a-level/macroeconomy-a-level.thumb.jpg?v=1788442428The macroeconomy (A Level)Look at one building going up. Someone is paying for steel, for concrete, for wages. But the story does not stop there. The builders take those wages home and…https://exercises.lol/video-media/a_level_economics/macroeconomy-a-level/macroeconomy-a-level.enzh.mp4?v=17884424285132026-08-15yes https://exercises.lol/videos/a_level_economics/government-macroeconomic-intervention-a2026-09-05https://exercises.lol/video-media/a_level_economics/government-macroeconomic-intervention-a/government-macroeconomic-intervention-a.thumb.jpg?v=1788591415Government macroeconomic intervention (A Level)Inside a building like this one, a small committee meets and changes a single number: the interest rate. Nothing is built. Nothing is bought. Yet within days…https://exercises.lol/video-media/a_level_economics/government-macroeconomic-intervention-a/government-macroeconomic-intervention-a.enzh.mp4?v=17885914154332026-08-15yes https://exercises.lol/videos/a_level_economics/international-economic-issues-a2026-09-03https://exercises.lol/video-media/a_level_economics/international-economic-issues-a/international-economic-issues-a.thumb.jpg?v=1788454418International economic issues (A Level)A country's money loses a fifth of its value overnight. Exports are suddenly cheap, imports suddenly dear, so the trade gap should close at once. It does not.…https://exercises.lol/video-media/a_level_economics/international-economic-issues-a/international-economic-issues-a.enzh.mp4?v=17884544185372026-08-15yes https://exercises.lol/videos/a_level_further_mathematics/further-pure-12026-09-05https://exercises.lol/video-media/a_level_further_mathematics/further-pure-1/further-pure-1.thumb.jpg?v=1788599489Further Pure Mathematics 1Here is a cubic equation, crossing the axis at three roots. Finding those roots exactly can be hard — or even impossible by hand. But here is a beautiful…https://exercises.lol/video-media/a_level_further_mathematics/further-pure-1/further-pure-1.enzh.mp4?v=17885994898682026-08-15yes https://exercises.lol/videos/a_level_further_mathematics/further-pure-22026-09-05https://exercises.lol/video-media/a_level_further_mathematics/further-pure-2/further-pure-2.thumb.jpg?v=1788601495Further Pure Mathematics 2Look at any hanging chain, any power line, any suspension cable. It always settles into one special curve. You might guess a parabola — but it is not. It is…https://exercises.lol/video-media/a_level_further_mathematics/further-pure-2/further-pure-2.enzh.mp4?v=17886014956892026-08-15yes https://exercises.lol/videos/a_level_further_mathematics/further-mechanics2026-09-05https://exercises.lol/video-media/a_level_further_mathematics/further-mechanics/further-mechanics.thumb.jpg?v=1788577738Further MechanicsThrow a ball, fire a jet of water, launch anything into the air — and it traces the same elegant curve: a parabola. The secret is to split the motion in two.…https://exercises.lol/video-media/a_level_further_mathematics/further-mechanics/further-mechanics.enzh.mp4?v=17885777384842026-08-15yes https://exercises.lol/videos/a_level_further_mathematics/further-prob-stats2026-09-05https://exercises.lol/video-media/a_level_further_mathematics/further-prob-stats/further-prob-stats.thumb.jpg?v=1788577663Further Probability & StatisticsDublin, nineteen-oh-eight. Inside the Guinness brewery, a young chemist named William Gosset faces a very practical problem. He can test only a few batches of…https://exercises.lol/video-media/a_level_further_mathematics/further-prob-stats/further-prob-stats.enzh.mp4?v=17885776634882026-08-15yes https://exercises.lol/videos/a_level_mathematics/pure-maths-12026-09-05https://exercises.lol/video-media/a_level_mathematics/pure-maths-1/pure-maths-1.thumb.jpg?v=1788578985Pure Mathematics 1Look at a great suspension bridge. Its huge cable is not a random shape — it hangs in a perfect parabola, a curve you can write with a single equation. The…https://exercises.lol/video-media/a_level_mathematics/pure-maths-1/pure-maths-1.enzh.mp4?v=178857898517212026-08-15yes https://exercises.lol/videos/a_level_mathematics/pure-maths-22026-09-05https://exercises.lol/video-media/a_level_mathematics/pure-maths-2/pure-maths-2.thumb.jpg?v=1788600133Pure Mathematics 2In two thousand eleven, an earthquake off Japan measured nine on the Richter scale. A smaller quake might measure six. Only three points apart — yet the first…https://exercises.lol/video-media/a_level_mathematics/pure-maths-2/pure-maths-2.enzh.mp4?v=17886001337522026-08-15yes https://exercises.lol/videos/a_level_mathematics/pure-maths-32026-09-05https://exercises.lol/video-media/a_level_mathematics/pure-maths-3/pure-maths-3.thumb.jpg?v=1788600282Pure Mathematics 3For centuries, mathematicians hit a wall: what is the square root of minus one? No ordinary number, squared, gives a negative. They called it impossible, and…https://exercises.lol/video-media/a_level_mathematics/pure-maths-3/pure-maths-3.enzh.mp4?v=17886002828152026-08-15yes https://exercises.lol/videos/a_level_mathematics/mechanics2026-09-05https://exercises.lol/video-media/a_level_mathematics/mechanics/mechanics.thumb.jpg?v=1788599822MechanicsPush a shopping trolley, and it speeds up. Push harder, and it speeds up faster. Push a heavier one with the same effort, and it barely moves. All of mechanics…https://exercises.lol/video-media/a_level_mathematics/mechanics/mechanics.enzh.mp4?v=17885998227582026-08-15yes https://exercises.lol/videos/a_level_mathematics/prob-stats-12026-09-05https://exercises.lol/video-media/a_level_mathematics/prob-stats-1/prob-stats-1.thumb.jpg?v=1788600007Probability & Statistics 1Roll a single die, and the result is anyone's guess. But roll it thousands of times, or measure the heights of thousands of people, and something remarkable…https://exercises.lol/video-media/a_level_mathematics/prob-stats-1/prob-stats-1.enzh.mp4?v=17886000076972026-08-15yes https://exercises.lol/videos/a_level_mathematics/prob-stats-22026-09-05https://exercises.lol/video-media/a_level_mathematics/prob-stats-2/prob-stats-2.thumb.jpg?v=1788599590Probability & Statistics 2Cambridge, the nineteen-twenties. At a garden party, a lady says something surprising. She can taste, she claims, whether the milk was poured into the cup…https://exercises.lol/video-media/a_level_mathematics/prob-stats-2/prob-stats-2.enzh.mp4?v=17885995906052026-08-15yes https://exercises.lol/videos/a_level_physics/gravitational-fields2026-09-05https://exercises.lol/video-media/a_level_physics/gravitational-fields/gravitational-fields.thumb.jpg?v=1788601313Gravitational FieldsAn apple falls from a tree. The Moon sails around the Earth. For thousands of years, no one saw any connection between them. Then Isaac Newton had one of the…https://exercises.lol/video-media/a_level_physics/gravitational-fields/gravitational-fields.enzh.mp4?v=17886013137342026-08-15yes https://exercises.lol/videos/a_level_physics/thermal-physics2026-09-05https://exercises.lol/video-media/a_level_physics/thermal-physics/thermal-physics.thumb.jpg?v=1788592054Thermal PhysicsTouch a metal spoon, then a wooden table, in the same room. The metal feels much colder. So it must be colder — right? Wrong. Bring a thermometer, and both…https://exercises.lol/video-media/a_level_physics/thermal-physics/thermal-physics.enzh.mp4?v=17885920547062026-08-15yes https://exercises.lol/videos/a_level_physics/internal-energy2026-09-05https://exercises.lol/video-media/a_level_physics/internal-energy/internal-energy.thumb.jpg?v=1788590752Internal EnergyPump up a bicycle tyre, quickly and hard, and something surprising happens: the pump gets hot. Warm enough to feel. You did not heat it with a flame. So where…https://exercises.lol/video-media/a_level_physics/internal-energy/internal-energy.enzh.mp4?v=17885907529262026-08-15yes https://exercises.lol/videos/a_level_physics/oscillations2026-09-05https://exercises.lol/video-media/a_level_physics/oscillations/oscillations.thumb.jpg?v=1788601901Oscillations & Simple Harmonic MotionIn 1940, a brand-new bridge opened across the Tacoma Narrows — long, elegant, and, as it turned out, dangerous. Within months, an ordinary wind set it heaving…https://exercises.lol/video-media/a_level_physics/oscillations/oscillations.enzh.mp4?v=17886019019122026-08-15yes https://exercises.lol/videos/a_level_physics/electric-fields2026-09-05https://exercises.lol/video-media/a_level_physics/electric-fields/electric-fields.thumb.jpg?v=1788595329Electric FieldsDeep inside a storm cloud, charge is building. Negative charge gathers at the base, positive charge on the ground below. Between them, in the empty air, an…https://exercises.lol/video-media/a_level_physics/electric-fields/electric-fields.enzh.mp4?v=17885953296612026-08-15yes https://exercises.lol/videos/a_level_physics/capacitance2026-09-05https://exercises.lol/video-media/a_level_physics/capacitance/capacitance.thumb.jpg?v=1788601509CapacitanceLook closely at a camera flash. Before the picture, a tiny part hums and whines for a second — you might even hear it. It is charging a capacitor, storing…https://exercises.lol/video-media/a_level_physics/capacitance/capacitance.enzh.mp4?v=17886015098882026-08-15yes https://exercises.lol/videos/a_level_physics/magnetic-fields2026-09-05https://exercises.lol/video-media/a_level_physics/magnetic-fields/magnetic-fields.thumb.jpg?v=1788594281Magnetic FieldsHigh above the poles, the sky comes alive — sheets of green light, rippling in the dark. This is the aurora. Its cause? Our planet is a giant magnet. Streams…https://exercises.lol/video-media/a_level_physics/magnetic-fields/magnetic-fields.enzh.mp4?v=17885942818002026-08-15yes https://exercises.lol/videos/a_level_physics/alternating-current2026-09-05https://exercises.lol/video-media/a_level_physics/alternating-current/alternating-current.thumb.jpg?v=1788590989Alternating CurrentThe electricity in your wall is restless. Fifty times every second — sometimes sixty — it reverses direction, surging one way, then the other. This is…https://exercises.lol/video-media/a_level_physics/alternating-current/alternating-current.enzh.mp4?v=17885909896782026-08-15yes https://exercises.lol/videos/a_level_physics/mass-energy2026-09-05https://exercises.lol/video-media/a_level_physics/mass-energy/mass-energy.thumb.jpg?v=1788580002Mass-Energy EquivalenceLook up at the Sun. Every single second, it turns four million tonnes of itself — gone, vanished — into pure energy. Not burned. Converted. That lost mass…https://exercises.lol/video-media/a_level_physics/mass-energy/mass-energy.enzh.mp4?v=17885800027882026-08-15yes https://exercises.lol/videos/a_level_physics/luminosity2026-09-05https://exercises.lol/video-media/a_level_physics/luminosity/luminosity.thumb.jpg?v=1788592055Luminosity & the CosmosThat star is a hundred trillion kilometres away. You will never touch it. You will never visit it. And yet, from its faint light alone — just the light that…https://exercises.lol/video-media/a_level_physics/luminosity/luminosity.enzh.mp4?v=17885920557612026-08-15yes https://exercises.lol/videos/ap_art_2d/elements-of-art2026-09-05https://exercises.lol/video-media/ap_art_2d/elements-of-art/elements-of-art.thumb.jpg?v=1788589711Elements of ArtLook at three famous pictures. A wave from Japan. A candle-lit room in England. A vase of sunflowers in France. Different countries, different centuries…https://exercises.lol/video-media/ap_art_2d/elements-of-art/elements-of-art.enzh.mp4?v=17885897114822026-08-15yes https://exercises.lol/videos/ap_art_2d/principles-of-design2026-09-05https://exercises.lol/video-media/ap_art_2d/principles-of-design/principles-of-design.thumb.jpg?v=1788587986Principles of DesignLook at this painting for three seconds. Where did your eye go first? Almost everyone looks at the same place — the two bright faces in the middle. That was…https://exercises.lol/video-media/ap_art_2d/principles-of-design/principles-of-design.enzh.mp4?v=17885879864402026-08-15yes https://exercises.lol/videos/ap_art_2d/2-d-media-materials2026-09-05https://exercises.lol/video-media/ap_art_2d/2-d-media-materials/2-d-media-materials.thumb.jpg?v=17885897972-D Media, Materials, and TechniquesLook closely. There is no grey ink in this drawing. Every soft shadow is made of separate lines, drawn one beside the other. Where the lines crowd together…https://exercises.lol/video-media/ap_art_2d/2-d-media-materials/2-d-media-materials.enzh.mp4?v=17885897974802026-08-15yes https://exercises.lol/videos/ap_art_2d/investigate-inquiry-and-the2026-09-05https://exercises.lol/video-media/ap_art_2d/investigate-inquiry-and-the/investigate-inquiry-and-the.thumb.jpg?v=1788586285Investigate: Inquiry and the Artistic ProcessTwo hundred years ago, a Japanese artist asked himself one question: how does one mountain look, seen from everywhere? The wave is enormous, filling more than…https://exercises.lol/video-media/ap_art_2d/investigate-inquiry-and-the/investigate-inquiry-and-the.enzh.mp4?v=17885862854462026-08-15yes https://exercises.lol/videos/ap_art_2d/make-practice-experimentation-and2026-09-05https://exercises.lol/video-media/ap_art_2d/make-practice-experimentation-and/make-practice-experimentation-and.thumb.jpg?v=1788590491Make: Practice, Experimentation, and RevisionLook at this pond. Claude Monet painted it again, and again, and again — about two hundred and fifty pictures of the same water, over thirty years. He was not…https://exercises.lol/video-media/ap_art_2d/make-practice-experimentation-and/make-practice-experimentation-and.enzh.mp4?v=17885904914482026-08-15yes https://exercises.lol/videos/ap_art_2d/present-communication-and-the2026-09-05https://exercises.lol/video-media/ap_art_2d/present-communication-and-the/present-communication-and-the.thumb.jpg?v=1788588993Present: Communication and the AP PortfolioYou have seen these three works before — but almost certainly not in a museum. You met them the way you are meeting them now: as pictures on a screen. Someone…https://exercises.lol/video-media/ap_art_2d/present-communication-and-the/present-communication-and-the.enzh.mp4?v=17885889934532026-08-15yes https://exercises.lol/videos/ap_biology/chemistry-of-life2026-09-05https://exercises.lol/video-media/ap_biology/chemistry-of-life/chemistry-of-life.thumb.jpg?v=1788598366Chemistry of LifeDrop an ice cube into a glass and it floats. That sounds ordinary, but it is strange. Almost every other solid sinks in its own liquid, because freezing packs…https://exercises.lol/video-media/ap_biology/chemistry-of-life/chemistry-of-life.enzh.mp4?v=17885983665642026-08-15yes https://exercises.lol/videos/ap_biology/cell-structure-and-function2026-09-05https://exercises.lol/video-media/ap_biology/cell-structure-and-function/cell-structure-and-function.thumb.jpg?v=1788587440Cell Structure and FunctionLook at a leaf under a microscope. You see rows of green boxes, and each box is packed with tiny green discs. Now look at a thin slice of onion. Neat brick…https://exercises.lol/video-media/ap_biology/cell-structure-and-function/cell-structure-and-function.enzh.mp4?v=17885874404852026-08-15yes https://exercises.lol/videos/ap_biology/cellular-energetics2026-09-05https://exercises.lol/video-media/ap_biology/cellular-energetics/cellular-energetics.thumb.jpg?v=1788585943Cellular EnergeticsLook at the washing powder in your cupboard. In warm water it removes a food stain in half an hour. In a lab, the same job would need strong acid and boiling…https://exercises.lol/video-media/ap_biology/cellular-energetics/cellular-energetics.enzh.mp4?v=17885859434782026-08-15yes https://exercises.lol/videos/ap_biology/cell-communication-and-cell2026-09-05https://exercises.lol/video-media/ap_biology/cell-communication-and-cell/cell-communication-and-cell.thumb.jpg?v=1788587871Cell Communication and Cell CycleLook closely. These are real cells, photographed in the middle of dividing. Inside your body, millions of new cells are made every second — skin, blood, gut…https://exercises.lol/video-media/ap_biology/cell-communication-and-cell/cell-communication-and-cell.enzh.mp4?v=17885878714542026-08-15yes https://exercises.lol/videos/ap_biology/heredity2026-09-05https://exercises.lol/video-media/ap_biology/heredity/heredity.thumb.jpg?v=1788586769HeredityTwo snails on the same tree. Same species, same bark, same weather. But look at the shells. One is pale with thin dark bands, the other dark with wide ones.…https://exercises.lol/video-media/ap_biology/heredity/heredity.enzh.mp4?v=17885867694732026-08-15yes https://exercises.lol/videos/ap_biology/gene-expression-and-regulation2026-09-05https://exercises.lol/video-media/ap_biology/gene-expression-and-regulation/gene-expression-and-regulation.thumb.jpg?v=1788598551Gene Expression and RegulationThat white thread in the tube is real DNA, pulled out of ordinary cells. It looks like nothing at all. But it holds every instruction your body will ever need.…https://exercises.lol/video-media/ap_biology/gene-expression-and-regulation/gene-expression-and-regulation.enzh.mp4?v=17885985515202026-08-15yes https://exercises.lol/videos/ap_biology/natural-selection2026-09-05https://exercises.lol/video-media/ap_biology/natural-selection/natural-selection.thumb.jpg?v=1788602497Natural SelectionThis is a dish of bacteria. Each white disc holds a different antibiotic — a drug made to kill them. Look at the clear rings. A wide ring means the drug still…https://exercises.lol/video-media/ap_biology/natural-selection/natural-selection.enzh.mp4?v=17886024974902026-08-15yes https://exercises.lol/videos/ap_biology/ecology2026-09-05https://exercises.lol/video-media/ap_biology/ecology/ecology.thumb.jpg?v=1788584717EcologyThis reef holds more kinds of life in one hectare than a whole province of farmland. Every fish depends on the coral, and the coral on tiny algae inside it.…https://exercises.lol/video-media/ap_biology/ecology/ecology.enzh.mp4?v=17885847174722026-08-15yes https://exercises.lol/videos/ap_calculus_ab/limits-continuity2026-09-05https://exercises.lol/video-media/ap_calculus_ab/limits-continuity/limits-continuity.thumb.jpg?v=1788600537Limits & ContinuityHere is a puzzle. A car's speedometer reads sixty kilometres per hour. But what does speed mean at a single instant? Speed is distance divided by time. Yet at…https://exercises.lol/video-media/ap_calculus_ab/limits-continuity/limits-continuity.enzh.mp4?v=17886005379752026-08-15yes https://exercises.lol/videos/ap_calculus_ab/defining-the-derivative2026-09-05https://exercises.lol/video-media/ap_calculus_ab/defining-the-derivative/defining-the-derivative.thumb.jpg?v=1788572628Defining the DerivativePicture a car's journey as a curve. Over a whole interval, we can measure its average speed — the slope of the straight line joining two points on the curve.…https://exercises.lol/video-media/ap_calculus_ab/defining-the-derivative/defining-the-derivative.enzh.mp4?v=17885726284732026-08-15yes https://exercises.lol/videos/ap_calculus_ab/chain-rule2026-09-05https://exercises.lol/video-media/ap_calculus_ab/chain-rule/chain-rule.thumb.jpg?v=1788577659The Chain RuleLook closely at this function: the sine of x squared. It is really two functions, one inside the other. First, square the input. Then take the sine of the…https://exercises.lol/video-media/ap_calculus_ab/chain-rule/chain-rule.enzh.mp4?v=17885776594082026-08-15yes https://exercises.lol/videos/ap_calculus_ab/derivative-in-context2026-09-05https://exercises.lol/video-media/ap_calculus_ab/derivative-in-context/derivative-in-context.thumb.jpg?v=1788600228Interpreting the Derivative in ContextNow that we can compute derivatives, we use them to describe the real world. A derivative is a rate of change. How fast is a population growing? How fast is a…https://exercises.lol/video-media/ap_calculus_ab/derivative-in-context/derivative-in-context.enzh.mp4?v=17886002284142026-08-15yes https://exercises.lol/videos/ap_calculus_ab/mean-value-theorem2026-09-05https://exercises.lol/video-media/ap_calculus_ab/mean-value-theorem/mean-value-theorem.thumb.jpg?v=1788600294Analysing Functions: The Mean Value TheoremImagine a road trip. Over two hours, you cover one hundred and twenty kilometres — an average speed of sixty. Here is a surprising promise: at some instant…https://exercises.lol/video-media/ap_calculus_ab/mean-value-theorem/mean-value-theorem.enzh.mp4?v=17886002946262026-08-15yes https://exercises.lol/videos/ap_calculus_ab/accumulation-integration2026-09-05https://exercises.lol/video-media/ap_calculus_ab/accumulation-integration/accumulation-integration.thumb.jpg?v=1788577225Accumulation & IntegrationDifferentiation found rates of change. Integration runs it in reverse: given a rate, it finds the total accumulated change. Here is the key picture. Water…https://exercises.lol/video-media/ap_calculus_ab/accumulation-integration/accumulation-integration.enzh.mp4?v=17885772256182026-08-15yes https://exercises.lol/videos/ap_calculus_ab/differential-equations2026-09-05https://exercises.lol/video-media/ap_calculus_ab/differential-equations/differential-equations.thumb.jpg?v=1788600069Differential EquationsMany real situations are described not by a formula, but by a rate. A population grows faster when it is larger. A hot drink cools faster when it is hotter. An…https://exercises.lol/video-media/ap_calculus_ab/differential-equations/differential-equations.enzh.mp4?v=17886000693232026-08-15yes https://exercises.lol/videos/ap_calculus_ab/applications-of-integration2026-09-05https://exercises.lol/video-media/ap_calculus_ab/applications-of-integration/applications-of-integration.thumb.jpg?v=1788578906Applications of IntegrationWhat is the average value of a function? Not the average of a few points — the average across a whole interval. Picture the area under the curve. Now flatten…https://exercises.lol/video-media/ap_calculus_ab/applications-of-integration/applications-of-integration.enzh.mp4?v=17885789063632026-08-15yes https://exercises.lol/videos/ap_calculus_bc/limits-continuity2026-09-05https://exercises.lol/video-media/ap_calculus_bc/limits-continuity/limits-continuity.thumb.jpg?v=1788589078Limits & ContinuityStart with a puzzle. A car's speedometer reads sixty kilometres per hour. But what does that mean at a single instant? Speed is distance over time. Yet in one…https://exercises.lol/video-media/ap_calculus_bc/limits-continuity/limits-continuity.enzh.mp4?v=178858907810762026-08-15yes https://exercises.lol/videos/ap_calculus_bc/defining-the-derivative2026-09-05https://exercises.lol/video-media/ap_calculus_bc/defining-the-derivative/defining-the-derivative.thumb.jpg?v=1788592382Defining the DerivativeDraw a journey as a curve. Pick two points, join them with a straight line, and its slope gives the average rate over an interval. But we want the rate at one…https://exercises.lol/video-media/ap_calculus_bc/defining-the-derivative/defining-the-derivative.enzh.mp4?v=17885923824712026-08-15yes https://exercises.lol/videos/ap_calculus_bc/chain-rule2026-09-05https://exercises.lol/video-media/ap_calculus_bc/chain-rule/chain-rule.thumb.jpg?v=1788586871The Chain RuleThink of two gears joined together. Turn the first one, and it drives the second. If the second turns three times as fast as the first, and the first turns…https://exercises.lol/video-media/ap_calculus_bc/chain-rule/chain-rule.enzh.mp4?v=17885868714772026-08-15yes https://exercises.lol/videos/ap_calculus_bc/derivative-in-context2026-09-05https://exercises.lol/video-media/ap_calculus_bc/derivative-in-context/derivative-in-context.thumb.jpg?v=1788588359Interpreting the Derivative in ContextA tank is draining. A cup of coffee is cooling. A city is growing. Every one of those sentences hides the same phrase. The rate at which something changes. And…https://exercises.lol/video-media/ap_calculus_bc/derivative-in-context/derivative-in-context.enzh.mp4?v=17885883595062026-08-15yes https://exercises.lol/videos/ap_calculus_bc/mean-value-theorem2026-09-05https://exercises.lol/video-media/ap_calculus_bc/mean-value-theorem/mean-value-theorem.thumb.jpg?v=1788588369Using the Mean Value TheoremYou drive two hundred kilometres in two hours. Your average speed was one hundred kilometres per hour. Now here is a claim. At some moment during that drive…https://exercises.lol/video-media/ap_calculus_bc/mean-value-theorem/mean-value-theorem.enzh.mp4?v=17885883695722026-08-15yes https://exercises.lol/videos/ap_calculus_bc/accumulation-integration2026-09-05https://exercises.lol/video-media/ap_calculus_bc/accumulation-integration/accumulation-integration.thumb.jpg?v=1788586795Exploring Accumulations of ChangeWater flows into a tank. The meter shows litres per minute. That is a rate of change. Now, how much water arrived in the first ten minutes? Draw the rate…https://exercises.lol/video-media/ap_calculus_bc/accumulation-integration/accumulation-integration.enzh.mp4?v=17885867956012026-08-15yes https://exercises.lol/videos/ap_calculus_bc/differential-equations2026-09-05https://exercises.lol/video-media/ap_calculus_bc/differential-equations/differential-equations.thumb.jpg?v=1788586631Modeling with Differential EquationsNormally you are handed a function and asked for its slope. A differential equation turns that around. You are handed a rule for the slope at every point, and…https://exercises.lol/video-media/ap_calculus_bc/differential-equations/differential-equations.enzh.mp4?v=17885866315062026-08-15yes https://exercises.lol/videos/ap_calculus_bc/applications-of-integration2026-09-05https://exercises.lol/video-media/ap_calculus_bc/applications-of-integration/applications-of-integration.thumb.jpg?v=1788587163Applications of IntegrationHere is a bumpy graph, and the area underneath it. Now imagine pouring that area into a rectangle over the same interval, and letting it level off. The height…https://exercises.lol/video-media/ap_calculus_bc/applications-of-integration/applications-of-integration.enzh.mp4?v=17885871635982026-08-15yes https://exercises.lol/videos/ap_calculus_bc/parametric-polar-vector2026-09-05https://exercises.lol/video-media/ap_calculus_bc/parametric-polar-vector/parametric-polar-vector.thumb.jpg?v=1788588383Parametric, Vector & PolarSome curves cannot be written as y equals a function of x. Think of a particle looping around, or a path that crosses itself — for one x there would be two y…https://exercises.lol/video-media/ap_calculus_bc/parametric-polar-vector/parametric-polar-vector.enzh.mp4?v=17885883833652026-08-15yes https://exercises.lol/videos/ap_calculus_bc/infinite-series2026-09-05https://exercises.lol/video-media/ap_calculus_bc/infinite-series/infinite-series.thumb.jpg?v=1788585834Infinite SeriesCan you add infinitely many numbers and get a finite answer? Surprisingly, yes. Add forever, and sometimes the total runs away to infinity — but sometimes it…https://exercises.lol/video-media/ap_calculus_bc/infinite-series/infinite-series.enzh.mp4?v=17885858344992026-08-15yes https://exercises.lol/videos/ap_chemistry/atomic-structure2026-09-05https://exercises.lol/video-media/ap_chemistry/atomic-structure/atomic-structure.thumb.jpg?v=1788600729Atomic Structure and PropertiesA chemical equation counts particles. Two of this react with one of that. But atoms are far too small to count, and there is no instrument that will hand you a…https://exercises.lol/video-media/ap_chemistry/atomic-structure/atomic-structure.enzh.mp4?v=17886007295592026-08-15yes https://exercises.lol/videos/ap_chemistry/compound-structure-and-properties2026-09-05https://exercises.lol/video-media/ap_chemistry/compound-structure-and-properties/compound-structure-and-properties.thumb.jpg?v=1788598174Compound Structure and PropertiesThree solids on a bench. Table salt. A diamond. A piece of copper. Hit the salt with a hammer and it shatters. The diamond scratches almost anything. The…https://exercises.lol/video-media/ap_chemistry/compound-structure-and-properties/compound-structure-and-properties.enzh.mp4?v=17885981745242026-08-15yes https://exercises.lol/videos/ap_chemistry/properties-of-substances-and2026-09-05https://exercises.lol/video-media/ap_chemistry/properties-of-substances-and/properties-of-substances-and.thumb.jpg?v=1788598275Properties of Substances and MixturesBoiling water. To make steam you must reach one hundred degrees Celsius. Methane has almost the same mass, and boils at minus one hundred and sixty-two.…https://exercises.lol/video-media/ap_chemistry/properties-of-substances-and/properties-of-substances-and.enzh.mp4?v=17885982756542026-08-15yes https://exercises.lol/videos/ap_chemistry/chemical-reactions2026-09-05https://exercises.lol/video-media/ap_chemistry/chemical-reactions/chemical-reactions.thumb.jpg?v=1788587050Chemical ReactionsA strip of magnesium metal. Touch it with a flame and it burns — combustion — with a light too bright to look at. What is left is not magnesium any more. It is…https://exercises.lol/video-media/ap_chemistry/chemical-reactions/chemical-reactions.enzh.mp4?v=17885870504612026-08-15yes https://exercises.lol/videos/ap_chemistry/kinetics2026-09-05https://exercises.lol/video-media/ap_chemistry/kinetics/kinetics.thumb.jpg?v=1788597738KineticsLook inside a car's exhaust pipe. This ceramic honeycomb is a catalytic converter. The gases rushing through it are poisonous. Left alone they would take years…https://exercises.lol/video-media/ap_chemistry/kinetics/kinetics.enzh.mp4?v=17885977384802026-08-15yes https://exercises.lol/videos/ap_chemistry/thermochemistry2026-09-05https://exercises.lol/video-media/ap_chemistry/thermochemistry/thermochemistry.thumb.jpg?v=1788598206ThermochemistrySqueeze this pack and in seconds it turns icy cold. Nothing is burning; nothing is cooling it from outside. A solid is simply dissolving in the water inside…https://exercises.lol/video-media/ap_chemistry/thermochemistry/thermochemistry.enzh.mp4?v=17885982065332026-08-15yes https://exercises.lol/videos/ap_chemistry/equilibrium2026-09-05https://exercises.lol/video-media/ap_chemistry/equilibrium/equilibrium.thumb.jpg?v=1788597983EquilibriumA chemical plant at dusk. Inside it, nitrogen from the air is turned into ammonia — the fertiliser that feeds about half the people alive today. But the…https://exercises.lol/video-media/ap_chemistry/equilibrium/equilibrium.enzh.mp4?v=17885979835042026-08-15yes https://exercises.lol/videos/ap_chemistry/acids-and-bases2026-09-05https://exercises.lol/video-media/ap_chemistry/acids-and-bases/acids-and-bases.thumb.jpg?v=1788598703Acids and BasesTwo strips of paper — one red, one blue. Dip them in a liquid and the colour changes, and that colour tells you whether the liquid is an acid or a base.…https://exercises.lol/video-media/ap_chemistry/acids-and-bases/acids-and-bases.enzh.mp4?v=17885987035032026-08-15yes https://exercises.lol/videos/ap_chemistry/thermodynamics-and-electrochemistry2026-09-05https://exercises.lol/video-media/ap_chemistry/thermodynamics-and-electrochemistry/thermodynamics-and-electrochemistry.thumb.jpg?v=1788584588Thermodynamics and ElectrochemistryTwo puzzles. Hold an ice cube: it melts in your hand, even though melting takes energy in. Now look at a diamond. Every diamond should slowly turn into…https://exercises.lol/video-media/ap_chemistry/thermodynamics-and-electrochemistry/thermodynamics-and-electrochemistry.enzh.mp4?v=17885845884962026-08-15yes https://exercises.lol/videos/ap_computer_science_a/objects-methods2026-09-05https://exercises.lol/video-media/ap_computer_science_a/objects-methods/objects-methods.thumb.jpg?v=1788619033Using Objects and MethodsHere are two Java programs. The first is missing a semicolon. The second divides seven by two and stores the answer in a whole number. The compiler stops the…https://exercises.lol/video-media/ap_computer_science_a/objects-methods/objects-methods.enzh.mp4?v=17886190339052026-08-15yes https://exercises.lol/videos/ap_computer_science_a/selection-iteration2026-09-05https://exercises.lol/video-media/ap_computer_science_a/selection-iteration/selection-iteration.thumb.jpg?v=1788618960Selection and IterationHere are three loops. They differ by one character each — a less-than instead of a less-than-or-equal, a greater-than instead of a less-than. The first runs…https://exercises.lol/video-media/ap_computer_science_a/selection-iteration/selection-iteration.enzh.mp4?v=17886189604782026-08-15yes https://exercises.lol/videos/ap_computer_science_a/class-creation2026-09-05https://exercises.lol/video-media/ap_computer_science_a/class-creation/class-creation.thumb.jpg?v=1788618942Class CreationHere is a student, stored as three loose variables: a name, a year, and a grade. That works. Now add a thousand students. You need three thousand variables…https://exercises.lol/video-media/ap_computer_science_a/class-creation/class-creation.enzh.mp4?v=17886189424452026-08-15yes https://exercises.lol/videos/ap_computer_science_a/data-collections2026-09-05https://exercises.lol/video-media/ap_computer_science_a/data-collections/data-collections.thumb.jpg?v=1788600069Data CollectionsTake one photo on your phone. To the computer it is not a picture at all — it is a grid of numbers, one for every pixel, about twelve million of them. Now try…https://exercises.lol/video-media/ap_computer_science_a/data-collections/data-collections.enzh.mp4?v=17886000698112026-08-15yes https://exercises.lol/videos/ap_computer_science_principles/creative-development2026-09-03https://exercises.lol/video-media/ap_computer_science_principles/creative-development/creative-development.thumb.jpg?v=1788442580Creative DevelopmentHere is a program that should print the average of two numbers. It runs. It does not crash. It prints an answer — and the answer is wrong. Give it four and six…https://exercises.lol/video-media/ap_computer_science_principles/creative-development/creative-development.enzh.mp4?v=17884425803022026-08-15yes https://exercises.lol/videos/ap_computer_science_principles/data2026-09-05https://exercises.lol/video-media/ap_computer_science_principles/data/data.thumb.jpg?v=1788600847DataPlay a song. What reaches your ear is a wave — smooth, continuous, never jumping from one value to the next. But your phone cannot store a wave. It can only…https://exercises.lol/video-media/ap_computer_science_principles/data/data.enzh.mp4?v=17886008474932026-08-15yes https://exercises.lol/videos/ap_computer_science_principles/algorithms-programming2026-09-05https://exercises.lol/video-media/ap_computer_science_principles/algorithms-programming/algorithms-programming.thumb.jpg?v=1788619471Algorithms and ProgrammingImagine a phone book with a million names, and you must find one. Check them one at a time, and you could be there all day. There is a way to find it in about…https://exercises.lol/video-media/ap_computer_science_principles/algorithms-programming/algorithms-programming.enzh.mp4?v=17886194715572026-08-15yes https://exercises.lol/videos/ap_computer_science_principles/computer-systems-and-networks2026-09-05https://exercises.lol/video-media/ap_computer_science_principles/computer-systems-and-networks/computer-systems-and-networks.thumb.jpg?v=1788601028Computer Systems and NetworksPeople call it the cloud. It is not a cloud. This box sits in somebody's home: a router, taking data from your phone and passing it on. This plug is the other…https://exercises.lol/video-media/ap_computer_science_principles/computer-systems-and-networks/computer-systems-and-networks.enzh.mp4?v=17886010284662026-08-15yes https://exercises.lol/videos/ap_computer_science_principles/impact-of-computing2026-09-05https://exercises.lol/video-media/ap_computer_science_principles/impact-of-computing/impact-of-computing.thumb.jpg?v=1788600970Impact of ComputingIn nineteen eighty-nine, one scientist built a small tool so physicists could swap papers faster. He was not planning any of this. A car that drives itself. A…https://exercises.lol/video-media/ap_computer_science_principles/impact-of-computing/impact-of-computing.enzh.mp4?v=17886009704922026-08-15yes https://exercises.lol/videos/ap_cybersecurity/intro-security2026-09-05https://exercises.lol/video-media/ap_cybersecurity/intro-security/intro-security.thumb.jpg?v=1788572531Introduction to SecurityYou can build a perfect wall. Unbreakable encryption, a firewall on every port, patches applied the day they ship. And an adversary can still walk straight…https://exercises.lol/video-media/ap_cybersecurity/intro-security/intro-security.enzh.mp4?v=17885725314742026-08-15yes https://exercises.lol/videos/ap_cybersecurity/securing-spaces2026-09-05https://exercises.lol/video-media/ap_cybersecurity/securing-spaces/securing-spaces.thumb.jpg?v=1788570615Securing SpacesA padlock on a chain. A camera above a door. Not computers, not code — but security. Because an adversary who cannot break your encryption has a simpler plan…https://exercises.lol/video-media/ap_cybersecurity/securing-spaces/securing-spaces.enzh.mp4?v=17885706155692026-08-15yes https://exercises.lol/videos/ap_cybersecurity/securing-networks2026-09-05https://exercises.lol/video-media/ap_cybersecurity/securing-networks/securing-networks.thumb.jpg?v=1788572847Securing NetworksYou send a message to your bank. It arrives. The reply comes back. Everything looks normal. But someone is sitting quietly between you, reading every message…https://exercises.lol/video-media/ap_cybersecurity/securing-networks/securing-networks.enzh.mp4?v=17885728475662026-08-15yes https://exercises.lol/videos/ap_cybersecurity/securing-devices2026-09-03https://exercises.lol/video-media/ap_cybersecurity/securing-devices/securing-devices.thumb.jpg?v=1788452014Securing DevicesIt is Monday morning in a busy hospital. In under a minute, the screens in the ward, the pharmacy and the records office all change. Every file on them is…https://exercises.lol/video-media/ap_cybersecurity/securing-devices/securing-devices.enzh.mp4?v=17884520145722026-08-15yes https://exercises.lol/videos/ap_cybersecurity/securing-applications-and-data2026-09-05https://exercises.lol/video-media/ap_cybersecurity/securing-applications-and-data/securing-applications-and-data.thumb.jpg?v=1788573257Securing Applications and DataA company spent a fortune on firewalls, locked doors and strong passwords. Then somebody typed a few strange characters into a login box — and the database…https://exercises.lol/video-media/ap_cybersecurity/securing-applications-and-data/securing-applications-and-data.enzh.mp4?v=17885732575862026-08-15yes https://exercises.lol/videos/ap_drawing/line-and-mark-making2026-09-05https://exercises.lol/video-media/ap_drawing/line-and-mark-making/line-and-mark-making.thumb.jpg?v=1788587224Line and Mark-MakingLook at these three drawings. No paint. No colour. Just a pencil, a pen, a needle on a metal plate. Every shadow you can see here is built out of marks: lines…https://exercises.lol/video-media/ap_drawing/line-and-mark-making/line-and-mark-making.enzh.mp4?v=17885872244642026-08-15yes https://exercises.lol/videos/ap_drawing/value-light-and-form2026-09-05https://exercises.lol/video-media/ap_drawing/value-light-and-form/value-light-and-form.thumb.jpg?v=1788587793Value, Light, and FormLook at this room. Almost all of it is dark. One small light is hidden behind the boy in the middle, and it is the only light in the picture. Yet you can still…https://exercises.lol/video-media/ap_drawing/value-light-and-form/value-light-and-form.enzh.mp4?v=17885877934582026-08-15yes https://exercises.lol/videos/ap_drawing/drawing-media-and-processes2026-09-05https://exercises.lol/video-media/ap_drawing/drawing-media-and-processes/drawing-media-and-processes.thumb.jpg?v=1788587513Drawing Media and ProcessesThree drawings here, and three materials. A portrait in pencil: it whispers, and it can always be rubbed out. A still life in charcoal: it shouts, it smudges…https://exercises.lol/video-media/ap_drawing/drawing-media-and-processes/drawing-media-and-processes.enzh.mp4?v=17885875135142026-08-15yes https://exercises.lol/videos/ap_english_language/unit-1-claims-evidence-and-the-rhetorical-situation2026-09-05https://exercises.lol/video-media/ap_english_language/unit-1-claims-evidence-and-the-rhetorical-situation/unit-1-claims-evidence-and-the-rhetorical-situation.thumb.jpg?v=1788567771Unit 1: Claims, Evidence, and the Rhetorical SituationHere is the single most common weak answer in this whole course. "The writer uses a rhetorical question." That sentence earns nothing, and it is what most…https://exercises.lol/video-media/ap_english_language/unit-1-claims-evidence-and-the-rhetorical-situation/unit-1-claims-evidence-and-the-rhetorical-situation.enzh.mp4?v=17885677713802026-09-03yes https://exercises.lol/videos/ap_english_language/unit-2-audience-thesis-and-supporting-evidence2026-09-05https://exercises.lol/video-media/ap_english_language/unit-2-audience-thesis-and-supporting-evidence/unit-2-audience-thesis-and-supporting-evidence.thumb.jpg?v=1788597867Unit 2: Audience, Thesis, and Supporting EvidenceHere is a test you can run on your own drafts in about ten seconds. Read one paragraph and ask: would this read identically to a completely different audience?…https://exercises.lol/video-media/ap_english_language/unit-2-audience-thesis-and-supporting-evidence/unit-2-audience-thesis-and-supporting-evidence.enzh.mp4?v=17885978673542026-09-03yes https://exercises.lol/videos/ap_english_language/unit-3-line-of-reasoning-and-methods-of-development2026-09-05https://exercises.lol/video-media/ap_english_language/unit-3-line-of-reasoning-and-methods-of-development/unit-3-line-of-reasoning-and-methods-of-development.thumb.jpg?v=1788598279Unit 3: Line of Reasoning and Methods of DevelopmentUnit 3 is where the course stops being about parts and starts being about structure, and here is the test that tells you whether you have any. Take your essay…https://exercises.lol/video-media/ap_english_language/unit-3-line-of-reasoning-and-methods-of-development/unit-3-line-of-reasoning-and-methods-of-development.enzh.mp4?v=17885982793562026-09-03yes https://exercises.lol/videos/ap_english_language/unit-4-introductions-conclusions-and-development2026-09-05https://exercises.lol/video-media/ap_english_language/unit-4-introductions-conclusions-and-development/unit-4-introductions-conclusions-and-development.thumb.jpg?v=1788600104Unit 4: Introductions, Conclusions, and DevelopmentUnit 4 covers the two positions in a text where a writer's choices are most visible — the beginning and the end. And it comes with a warning about your own…https://exercises.lol/video-media/ap_english_language/unit-4-introductions-conclusions-and-development/unit-4-introductions-conclusions-and-development.enzh.mp4?v=17886001043172026-09-03yes https://exercises.lol/videos/ap_english_language/unit-5-organization-coherence-and-style2026-09-05https://exercises.lol/video-media/ap_english_language/unit-5-organization-coherence-and-style/unit-5-organization-coherence-and-style.thumb.jpg?v=1788597818Unit 5: Organization, Coherence, and StyleThe CED's statement of the body paragraph is exact and worth memorising. The body paragraphs of a written argument make claims, support them with evidence, and…https://exercises.lol/video-media/ap_english_language/unit-5-organization-coherence-and-style/unit-5-organization-coherence-and-style.enzh.mp4?v=17885978183412026-09-03yes https://exercises.lol/videos/ap_english_language/unit-6-evidence-thesis-and-stylistic-choices2026-09-05https://exercises.lol/video-media/ap_english_language/unit-6-evidence-thesis-and-stylistic-choices/unit-6-evidence-thesis-and-stylistic-choices.thumb.jpg?v=1788599914Unit 6: Evidence, Thesis, and Stylistic ChoicesUnit 6 is the synthesis unit, and it contains the single sharpest distinction in the course. A position and a perspective are different. Sources may hold the…https://exercises.lol/video-media/ap_english_language/unit-6-evidence-thesis-and-stylistic-choices/unit-6-evidence-thesis-and-stylistic-choices.enzh.mp4?v=17885999143202026-09-03yes https://exercises.lol/videos/ap_english_language/unit-7-qualifying-arguments-syntax-and-conventions2026-09-05https://exercises.lol/video-media/ap_english_language/unit-7-qualifying-arguments-syntax-and-conventions/unit-7-qualifying-arguments-syntax-and-conventions.thumb.jpg?v=1788598334Unit 7: Qualifying Arguments, Syntax, and ConventionsMost students assume a stronger-sounding claim scores better. The opposite is true, and it is easy to see why. An unqualified claim is easy to defeat with one…https://exercises.lol/video-media/ap_english_language/unit-7-qualifying-arguments-syntax-and-conventions/unit-7-qualifying-arguments-syntax-and-conventions.enzh.mp4?v=17885983343792026-09-03yes https://exercises.lol/videos/ap_english_language/unit-8-audience-tone-and-sentence-craft2026-09-05https://exercises.lol/video-media/ap_english_language/unit-8-audience-tone-and-sentence-craft/unit-8-audience-tone-and-sentence-craft.thumb.jpg?v=1788599990Unit 8: Audience, Tone, and Sentence CraftA writer's style is the mix of word choice, syntax and conventions employed by that writer. Style is a composite — which is why "the writer's style is formal"…https://exercises.lol/video-media/ap_english_language/unit-8-audience-tone-and-sentence-craft/unit-8-audience-tone-and-sentence-craft.enzh.mp4?v=17885999903442026-09-03yes https://exercises.lol/videos/ap_english_language/unit-9-refining-qualified-arguments2026-09-05https://exercises.lol/video-media/ap_english_language/unit-9-refining-qualified-arguments/unit-9-refining-qualified-arguments.thumb.jpg?v=1788596939Unit 9: Refining Qualified ArgumentsUnit 9 is short, and it is the course's final move: how to handle the arguments that oppose yours. Everything here is directly rewarded on the exam, and the…https://exercises.lol/video-media/ap_english_language/unit-9-refining-qualified-arguments/unit-9-refining-qualified-arguments.enzh.mp4?v=17885969392902026-09-03yes https://exercises.lol/videos/ap_english_literature/unit-1-short-fiction-i2026-09-05https://exercises.lol/video-media/ap_english_literature/unit-1-short-fiction-i/unit-1-short-fiction-i.thumb.jpg?v=1788570200Unit 1: Short Fiction IAP English Literature reads texts in three genres across nine units — short fiction, poetry, and longer fiction or drama — each visited three times at…https://exercises.lol/video-media/ap_english_literature/unit-1-short-fiction-i/unit-1-short-fiction-i.enzh.mp4?v=17885702004032026-09-03yes https://exercises.lol/videos/ap_english_literature/unit-2-poetry-i2026-09-05https://exercises.lol/video-media/ap_english_literature/unit-2-poetry-i/unit-2-poetry-i.thumb.jpg?v=1788597527Unit 2: Poetry IUnit 2 is the course's first poetry unit, and it adds two things to Unit 1's toolkit: structure as an object of analysis, and figurative language handled…https://exercises.lol/video-media/ap_english_literature/unit-2-poetry-i/unit-2-poetry-i.enzh.mp4?v=17885975273702026-09-03yes https://exercises.lol/videos/ap_english_literature/unit-3-longer-fiction-or-drama-i2026-09-05https://exercises.lol/video-media/ap_english_literature/unit-3-longer-fiction-or-drama-i/unit-3-longer-fiction-or-drama-i.thumb.jpg?v=1788597197Unit 3: Longer Fiction or Drama IUnit 3 is the first longer-fiction-or-drama unit, and the thing to notice is that the length changes what is analysable. Three things become available that a…https://exercises.lol/video-media/ap_english_literature/unit-3-longer-fiction-or-drama-i/unit-3-longer-fiction-or-drama-i.enzh.mp4?v=17885971975152026-09-03yes https://exercises.lol/videos/ap_english_literature/unit-4-short-fiction-ii2026-09-05https://exercises.lol/video-media/ap_english_literature/unit-4-short-fiction-ii/unit-4-short-fiction-ii.thumb.jpg?v=1788597340Unit 4: Short Fiction IIUnit 4 returns to short fiction with a much larger toolkit, and its two most valuable additions are narrative distance and the idea that choices reveal values.…https://exercises.lol/video-media/ap_english_literature/unit-4-short-fiction-ii/unit-4-short-fiction-ii.enzh.mp4?v=17885973406462026-09-03yes https://exercises.lol/videos/ap_english_literature/unit-5-poetry-ii2026-09-05https://exercises.lol/video-media/ap_english_literature/unit-5-poetry-ii/unit-5-poetry-ii.thumb.jpg?v=1788597847Unit 5: Poetry IIUnit 5 is the second poetry unit, and it does two things: it names the forms a poem can take, and it completes the figurative toolkit. Closed forms include…https://exercises.lol/video-media/ap_english_literature/unit-5-poetry-ii/unit-5-poetry-ii.enzh.mp4?v=17885978475432026-09-03yes https://exercises.lol/videos/ap_english_literature/unit-6-longer-fiction-or-drama-ii2026-09-05https://exercises.lol/video-media/ap_english_literature/unit-6-longer-fiction-or-drama-ii/unit-6-longer-fiction-or-drama-ii.thumb.jpg?v=1788598164Unit 6: Longer Fiction or Drama IIUnit 6 is the second longer-fiction-or-drama unit, and it adds the two most sophisticated tools in the course: narrator reliability and the symbol. It opens…https://exercises.lol/video-media/ap_english_literature/unit-6-longer-fiction-or-drama-ii/unit-6-longer-fiction-or-drama-ii.enzh.mp4?v=17885981645742026-09-03yes https://exercises.lol/videos/ap_english_literature/unit-7-short-fiction-iii2026-09-05https://exercises.lol/video-media/ap_english_literature/unit-7-short-fiction-iii/unit-7-short-fiction-iii.thumb.jpg?v=1788597836Unit 7: Short Fiction IIIUnit 7 is the last short-fiction unit, and it sharpens two things: how change happens in a character, and pacing as a deliberate manipulation of time. Take…https://exercises.lol/video-media/ap_english_literature/unit-7-short-fiction-iii/unit-7-short-fiction-iii.enzh.mp4?v=17885978365412026-09-03yes https://exercises.lol/videos/ap_english_literature/unit-8-poetry-iii2026-09-05https://exercises.lol/video-media/ap_english_literature/unit-8-poetry-iii/unit-8-poetry-iii.thumb.jpg?v=1788598940Unit 8: Poetry IIIUnit 8 is the last poetry unit and it handles the hardest material in the course: the family of devices built on contradiction. But it opens with the most…https://exercises.lol/video-media/ap_english_literature/unit-8-poetry-iii/unit-8-poetry-iii.enzh.mp4?v=17885989405202026-09-03yes https://exercises.lol/videos/ap_english_literature/unit-9-longer-fiction-or-drama-iii2026-09-05https://exercises.lol/video-media/ap_english_literature/unit-9-longer-fiction-or-drama-iii/unit-9-longer-fiction-or-drama-iii.thumb.jpg?v=1788600571Unit 9: Longer Fiction or Drama IIIUnit 9 is the final unit, and its subject is how texts end — and what an ending lets a reader conclude about the whole work. It opens with the interpretive…https://exercises.lol/video-media/ap_english_literature/unit-9-longer-fiction-or-drama-iii/unit-9-longer-fiction-or-drama-iii.enzh.mp4?v=17886005714762026-09-03yes https://exercises.lol/videos/ap_environmental_science/biodiversity2026-09-05https://exercises.lol/video-media/ap_environmental_science/biodiversity/biodiversity.thumb.jpg?v=1788580697The Living World: BiodiversityA volcano pushes a new island up out of the sea. At first there is nothing on it — bare rock, no soil, no life at all. Fifty years later, it is green. So how…https://exercises.lol/video-media/ap_environmental_science/biodiversity/biodiversity.enzh.mp4?v=17885806974772026-08-15yes https://exercises.lol/videos/ap_environmental_science/populations2026-09-05https://exercises.lol/video-media/ap_environmental_science/populations/populations.thumb.jpg?v=1788580652PopulationsIn 1944, twenty-nine reindeer were released onto a small island. There were no predators, and the ground was thick with moss. Within twenty years there were…https://exercises.lol/video-media/ap_environmental_science/populations/populations.enzh.mp4?v=17885806524642026-08-15yes https://exercises.lol/videos/ap_environmental_science/earth-systems2026-09-05https://exercises.lol/video-media/ap_environmental_science/earth-systems/earth-systems.thumb.jpg?v=1788580596Earth Systems and ResourcesTwo towns, forty kilometres apart, on opposite sides of one mountain range. One of them gets three metres of rain a year — a rainforest. The other gets less…https://exercises.lol/video-media/ap_environmental_science/earth-systems/earth-systems.enzh.mp4?v=17885805964482026-08-15yes https://exercises.lol/videos/ap_environmental_science/land-and-water-use2026-09-05https://exercises.lol/video-media/ap_environmental_science/land-and-water-use/land-and-water-use.thumb.jpg?v=1788580870Land and Water UseThree ordinary places. A logging truck carrying trees that stood here this morning. A pit so wide you could see it from space. A city spreading over the…https://exercises.lol/video-media/ap_environmental_science/land-and-water-use/land-and-water-use.enzh.mp4?v=17885808708162026-08-15yes https://exercises.lol/videos/ap_environmental_science/energy-resources-and-consumption2026-09-05https://exercises.lol/video-media/ap_environmental_science/energy-resources-and-consumption/energy-resources-and-consumption.thumb.jpg?v=1788582845Energy Resources and ConsumptionLook at this hole in the ground. A machine digs out soft brown coal, and the power station behind it burns it the same day. Now look at this: three towers on a…https://exercises.lol/video-media/ap_environmental_science/energy-resources-and-consumption/energy-resources-and-consumption.enzh.mp4?v=17885828455532026-08-15yes https://exercises.lol/videos/ap_environmental_science/atmospheric-pollution2026-09-05https://exercises.lol/video-media/ap_environmental_science/atmospheric-pollution/atmospheric-pollution.thumb.jpg?v=1788580435Atmospheric PollutionLook at this city. You cannot see the buildings, because you can see the air. Now step inside a kitchen, where one cooking fire fills the room with smoke. Now…https://exercises.lol/video-media/ap_environmental_science/atmospheric-pollution/atmospheric-pollution.enzh.mp4?v=17885804354812026-08-15yes https://exercises.lol/videos/ap_environmental_science/aquatic-and-terrestrial-pollution2026-09-05https://exercises.lol/video-media/ap_environmental_science/aquatic-and-terrestrial-pollution/aquatic-and-terrestrial-pollution.thumb.jpg?v=1788580565Aquatic and Terrestrial PollutionLook at this pond. It is bright green, and it is full of life. Every fish in it is dead. Now look at this hill. It is not a hill. It is our rubbish, buried.…https://exercises.lol/video-media/ap_environmental_science/aquatic-and-terrestrial-pollution/aquatic-and-terrestrial-pollution.enzh.mp4?v=17885805655172026-08-15yes https://exercises.lol/videos/ap_environmental_science/global-change2026-09-05https://exercises.lol/video-media/ap_environmental_science/global-change/global-change.thumb.jpg?v=1788580813Global ChangeIn nineteen eighty-five, scientists studying the sky above Antarctica found something frightening: a hole in the ozone layer, the thin shield that keeps the…https://exercises.lol/video-media/ap_environmental_science/global-change/global-change.enzh.mp4?v=17885808134942026-08-15yes https://exercises.lol/videos/ap_european_history/unit-1-renaissance-and-exploration2026-09-05https://exercises.lol/video-media/ap_european_history/unit-1-renaissance-and-exploration/unit-1-renaissance-and-exploration.thumb.jpg?v=1788581716Unit 1: Renaissance and ExplorationTwo words in the CED tell you how this entire course is marked, and they appear in Unit 1. Varying degrees. The struggle for sovereignty within and among…https://exercises.lol/video-media/ap_european_history/unit-1-renaissance-and-exploration/unit-1-renaissance-and-exploration.enzh.mp4?v=17885817166042026-09-03yes https://exercises.lol/videos/ap_european_history/unit-2-age-of-reformation2026-09-05https://exercises.lol/video-media/ap_european_history/unit-2-age-of-reformation/unit-2-age-of-reformation.thumb.jpg?v=1788580952Unit 2: Age of ReformationThere is one way students reliably lose marks in this unit, and it is a study habit rather than a gap in knowledge. They keep religion and politics in separate…https://exercises.lol/video-media/ap_european_history/unit-2-age-of-reformation/unit-2-age-of-reformation.enzh.mp4?v=17885809524812026-09-03yes https://exercises.lol/videos/ap_european_history/unit-3-absolutism-and-constitutionalism2026-09-05https://exercises.lol/video-media/ap_european_history/unit-3-absolutism-and-constitutionalism/unit-3-absolutism-and-constitutionalism.thumb.jpg?v=1788595887Unit 3: Absolutism and ConstitutionalismContextualizing state building starts with one phrase: the struggle for sovereignty kept producing varying degrees of political centralisation. Everything in…https://exercises.lol/video-media/ap_european_history/unit-3-absolutism-and-constitutionalism/unit-3-absolutism-and-constitutionalism.enzh.mp4?v=17885958874402026-09-03yes https://exercises.lol/videos/ap_european_history/unit-4-scientific-philosophical-and-political-developments2026-09-05https://exercises.lol/video-media/ap_european_history/unit-4-scientific-philosophical-and-political-developments/unit-4-scientific-philosophical-and-political-developments.thumb.jpg?v=1788590667Unit 4: Scientific, Philosophical, and Political DevelopmentsOne sentence contains this entire unit, and it is worth learning in the CED's own words. The spread of Scientific Revolution concepts and practices, and the…https://exercises.lol/video-media/ap_european_history/unit-4-scientific-philosophical-and-political-developments/unit-4-scientific-philosophical-and-political-developments.enzh.mp4?v=17885906674732026-09-03yes https://exercises.lol/videos/ap_european_history/unit-5-conflict-crisis-and-reaction2026-09-05https://exercises.lol/video-media/ap_european_history/unit-5-conflict-crisis-and-reaction/unit-5-conflict-crisis-and-reaction.thumb.jpg?v=1788596017Unit 5: Conflict, Crisis, and ReactionContextualizing eighteenth-century states means holding four things together: global commercial competition, the French Revolution, Napoleon, and the…https://exercises.lol/video-media/ap_european_history/unit-5-conflict-crisis-and-reaction/unit-5-conflict-crisis-and-reaction.enzh.mp4?v=17885960174412026-09-03yes https://exercises.lol/videos/ap_european_history/unit-6-industrialization-and-its-effects2026-09-05https://exercises.lol/video-media/ap_european_history/unit-6-industrialization-and-its-effects/unit-6-industrialization-and-its-effects.thumb.jpg?v=1788581093Unit 6: Industrialization and Its EffectsOne claim is the spine of this unit. Political revolutions and the complications of industrialisation triggered a range of ideological, governmental and…https://exercises.lol/video-media/ap_european_history/unit-6-industrialization-and-its-effects/unit-6-industrialization-and-its-effects.enzh.mp4?v=17885810935542026-09-03yes https://exercises.lol/videos/ap_european_history/unit-7-19th-century-perspectives-and-political-developments2026-09-05https://exercises.lol/video-media/ap_european_history/unit-7-19th-century-perspectives-and-political-developments/unit-7-19th-century-perspectives-and-political-developments.thumb.jpg?v=1788595717Unit 7: 19th-Century Perspectives and Political DevelopmentsContextualizing nineteenth-century perspectives covers about eighteen hundred and fifteen to nineteen hundred and fourteen. If you learn one thing from this…https://exercises.lol/video-media/ap_european_history/unit-7-19th-century-perspectives-and-political-developments/unit-7-19th-century-perspectives-and-political-developments.enzh.mp4?v=17885957175122026-09-03yes https://exercises.lol/videos/ap_european_history/unit-8-20th-century-global-conflicts2026-09-05https://exercises.lol/video-media/ap_european_history/unit-8-20th-century-global-conflicts/unit-8-20th-century-global-conflicts.thumb.jpg?v=1788581070Unit 8: 20th-Century Global ConflictsLearn the chain, and this unit becomes navigable. War. Settlement. Economic collapse. Radical movements. Failed appeasement. War again. Most questions ask…https://exercises.lol/video-media/ap_european_history/unit-8-20th-century-global-conflicts/unit-8-20th-century-global-conflicts.enzh.mp4?v=17885810705472026-09-03yes https://exercises.lol/videos/ap_european_history/unit-9-cold-war-and-contemporary-europe2026-09-05https://exercises.lol/video-media/ap_european_history/unit-9-cold-war-and-contemporary-europe/unit-9-cold-war-and-contemporary-europe.thumb.jpg?v=1788581780Unit 9: Cold War and Contemporary EuropeThis unit has two halves that must be held together. Division, until 1991. And integration, running alongside it and then beyond it. They are not sequential…https://exercises.lol/video-media/ap_european_history/unit-9-cold-war-and-contemporary-europe/unit-9-cold-war-and-contemporary-europe.enzh.mp4?v=17885817805772026-09-03yes https://exercises.lol/videos/ap_human_geography/thinking-geographically2026-09-05https://exercises.lol/video-media/ap_human_geography/thinking-geographically/thinking-geographically.thumb.jpg?v=1788579296Thinking GeographicallyLook at Greenland on a classroom world map. It looks about the size of Africa. It is not. Africa is fourteen times larger. <slow>The map is not lying to you by…https://exercises.lol/video-media/ap_human_geography/thinking-geographically/thinking-geographically.enzh.mp4?v=17885792964942026-08-15yes https://exercises.lol/videos/ap_human_geography/population-and-migration-patterns2026-09-05https://exercises.lol/video-media/ap_human_geography/population-and-migration-patterns/population-and-migration-patterns.thumb.jpg?v=1788573895Population and Migration Patterns and ProcessesEight billion people live on this planet. Now look at this street. At one crossing in Tokyo, hundreds of them share a space the size of a school hall.…https://exercises.lol/video-media/ap_human_geography/population-and-migration-patterns/population-and-migration-patterns.enzh.mp4?v=17885738955282026-08-15yes https://exercises.lol/videos/ap_human_geography/cultural-patterns-and-processes2026-09-05https://exercises.lol/video-media/ap_human_geography/cultural-patterns-and-processes/cultural-patterns-and-processes.thumb.jpg?v=1788573843Cultural Patterns and ProcessesThis gate stands over a street in Seattle, in the United States. But the roof, the colours and the writing all come from China, nearly ten thousand kilometres…https://exercises.lol/video-media/ap_human_geography/cultural-patterns-and-processes/cultural-patterns-and-processes.enzh.mp4?v=17885738434692026-08-15yes https://exercises.lol/videos/ap_human_geography/political-patterns-and-processes2026-09-05https://exercises.lol/video-media/ap_human_geography/political-patterns-and-processes/political-patterns-and-processes.thumb.jpg?v=1788584844Political Patterns and ProcessesHere is a fence. It runs across open ground all the way to the horizon. On the far side stands a city — the same dry land, the same sky. And here is the hall…https://exercises.lol/video-media/ap_human_geography/political-patterns-and-processes/political-patterns-and-processes.enzh.mp4?v=17885848444912026-08-15yes https://exercises.lol/videos/ap_human_geography/agriculture-and-rural-land2026-09-05https://exercises.lol/video-media/ap_human_geography/agriculture-and-rural-land/agriculture-and-rural-land.thumb.jpg?v=1788577755Agriculture and Rural Land-Use Patterns and ProcessesTwo farmers. The same job: grow food. Completely different worlds. One drives a machine across a field so wide you cannot see the end of it, and every grain…https://exercises.lol/video-media/ap_human_geography/agriculture-and-rural-land/agriculture-and-rural-land.enzh.mp4?v=17885777555122026-08-15yes https://exercises.lol/videos/ap_human_geography/cities-and-urban-land2026-09-05https://exercises.lol/video-media/ap_human_geography/cities-and-urban-land/cities-and-urban-land.thumb.jpg?v=1788575052Cities and Urban Land-Use Patterns and ProcessesMore than half of the people on Earth now live in a city, and that share still grows. A city can pull in money, jobs and ideas from the whole planet. And on a…https://exercises.lol/video-media/ap_human_geography/cities-and-urban-land/cities-and-urban-land.enzh.mp4?v=17885750524942026-08-15yes https://exercises.lol/videos/ap_human_geography/industrial-and-economic-development2026-09-05https://exercises.lol/video-media/ap_human_geography/industrial-and-economic-development/industrial-and-economic-development.thumb.jpg?v=1788589357Industrial and Economic Development Patterns and ProcessesAlmost everything in the room around you was made in a factory and carried here on a ship. Two hundred and fifty years ago, almost nobody lived like this. Then…https://exercises.lol/video-media/ap_human_geography/industrial-and-economic-development/industrial-and-economic-development.enzh.mp4?v=17885893574822026-08-15yes https://exercises.lol/videos/ap_macroeconomics/basic-economic-concepts2026-09-05https://exercises.lol/video-media/ap_macroeconomics/basic-economic-concepts/basic-economic-concepts.thumb.jpg?v=1788601371Basic Economic ConceptsHere is a result that feels wrong the first time you meet it. Suppose you are faster than your friend at writing code and faster at writing documentation. You…https://exercises.lol/video-media/ap_macroeconomics/basic-economic-concepts/basic-economic-concepts.enzh.mp4?v=17886013714492026-08-15yes https://exercises.lol/videos/ap_macroeconomics/economic-indicators-and-the2026-09-05https://exercises.lol/video-media/ap_macroeconomics/economic-indicators-and-the/economic-indicators-and-the.thumb.jpg?v=1788601673Economic Indicators and the Business CycleTwo ordinary scenes. A supermarket aisle, where the same basket of food costs more than it did last year. And a long queue of people, waiting. Neither is an…https://exercises.lol/video-media/ap_macroeconomics/economic-indicators-and-the/economic-indicators-and-the.enzh.mp4?v=17886016735972026-08-15yes https://exercises.lol/videos/ap_macroeconomics/national-income-and-price2026-09-05https://exercises.lol/video-media/ap_macroeconomics/national-income-and-price/national-income-and-price.thumb.jpg?v=1788579555National Income and Price DeterminationA government spends ten billion dollars on new railways. How much does the country's output rise? Not ten billion. It can rise by fifty billion. Money spent by…https://exercises.lol/video-media/ap_macroeconomics/national-income-and-price/national-income-and-price.enzh.mp4?v=17885795555302026-08-15yes https://exercises.lol/videos/ap_macroeconomics/financial-sector2026-09-05https://exercises.lol/video-media/ap_macroeconomics/financial-sector/financial-sector.thumb.jpg?v=1788572940Financial SectorLook at the money in your hand. It is only paper. It is worth something because everyone agrees to accept it. And out of millions of those agreements grows…https://exercises.lol/video-media/ap_macroeconomics/financial-sector/financial-sector.enzh.mp4?v=17885729404752026-08-15yes https://exercises.lol/videos/ap_macroeconomics/long-run-consequences-of2026-09-05https://exercises.lol/video-media/ap_macroeconomics/long-run-consequences-of/long-run-consequences-of.thumb.jpg?v=1788601434Long-Run Consequences of Stabilization PoliciesA government wants to end a recession fast. It spends more, cuts taxes, and the central bank makes borrowing cheap. It works — output rises, jobs come back.…https://exercises.lol/video-media/ap_macroeconomics/long-run-consequences-of/long-run-consequences-of.enzh.mp4?v=17886014345082026-08-15yes https://exercises.lol/videos/ap_macroeconomics/open-economy-international-trade2026-09-05https://exercises.lol/video-media/ap_macroeconomics/open-economy-international-trade/open-economy-international-trade.thumb.jpg?v=1788601581Open Economy—International Trade and FinanceCheck the label on almost anything you own. Made somewhere else. It crossed an ocean in a steel box like these, and somebody paid for it in a different money.…https://exercises.lol/video-media/ap_macroeconomics/open-economy-international-trade/open-economy-international-trade.enzh.mp4?v=17886015814802026-08-15yes https://exercises.lol/videos/ap_microeconomics/basic-economic-concepts2026-09-05https://exercises.lol/video-media/ap_microeconomics/basic-economic-concepts/basic-economic-concepts.thumb.jpg?v=1788576707Basic Economic ConceptsA day has only twenty-four hours. Think what you want to fit into one: sleep, school, homework, sport, time with friends. Add it up honestly and it comes to…https://exercises.lol/video-media/ap_microeconomics/basic-economic-concepts/basic-economic-concepts.enzh.mp4?v=17885767075132026-08-15yes https://exercises.lol/videos/ap_microeconomics/supply-and-demand2026-09-05https://exercises.lol/video-media/ap_microeconomics/supply-and-demand/supply-and-demand.thumb.jpg?v=1788579604Supply and DemandWhy does a cup of coffee cost what it costs? Nobody decided it. There is no committee and no official price list. There are only buyers, who want more when it…https://exercises.lol/video-media/ap_microeconomics/supply-and-demand/supply-and-demand.enzh.mp4?v=17885796046392026-08-15yes https://exercises.lol/videos/ap_microeconomics/production-and-cost2026-09-05https://exercises.lol/video-media/ap_microeconomics/production-and-cost/production-and-cost.thumb.jpg?v=1788572383Production, Cost & Perfect CompetitionPicture a small bakery with one kitchen and one oven. Hire your first baker and you get thirty extra loaves a day. Hire a second and you get twenty-six more. A…https://exercises.lol/video-media/ap_microeconomics/production-and-cost/production-and-cost.enzh.mp4?v=17885723835352026-08-15yes https://exercises.lol/videos/ap_microeconomics/imperfect-competition2026-09-05https://exercises.lol/video-media/ap_microeconomics/imperfect-competition/imperfect-competition.thumb.jpg?v=1788601527Imperfect CompetitionLook outside the textbook. A car company sets its own price. Your city has one water supplier, and no second one to choose. These firms do not take the price…https://exercises.lol/video-media/ap_microeconomics/imperfect-competition/imperfect-competition.enzh.mp4?v=17886015275112026-08-15yes https://exercises.lol/videos/ap_microeconomics/factor-markets2026-09-05https://exercises.lol/video-media/ap_microeconomics/factor-markets/factor-markets.thumb.jpg?v=1788572231Factor MarketsTwo workers. One sews shirts in a clothing factory. The other builds cars on an assembly line. The second earns far more. Why? In this unit the firm is the…https://exercises.lol/video-media/ap_microeconomics/factor-markets/factor-markets.enzh.mp4?v=17885722314762026-08-15yes https://exercises.lol/videos/ap_microeconomics/market-failure-and-the2026-09-05https://exercises.lol/video-media/ap_microeconomics/market-failure-and-the/market-failure-and-the.thumb.jpg?v=1788572448Market Failure and the Role of GovernmentLook at this factory. Somebody bought what it makes, and somebody was paid to make it. Both sides are happy with the price. But the smoke is not in that price.…https://exercises.lol/video-media/ap_microeconomics/market-failure-and-the/market-failure-and-the.enzh.mp4?v=17885724485002026-08-15yes https://exercises.lol/videos/ap_physics_1/kinematics2026-09-03https://exercises.lol/video-media/ap_physics_1/kinematics/kinematics.thumb.jpg?v=1788432450KinematicsTwo balls leave a table at the same moment. One is simply dropped. The other is fired sideways, hard. Which one hits the floor first? <slow>They land…https://exercises.lol/video-media/ap_physics_1/kinematics/kinematics.enzh.mp4?v=17884324505442026-08-15yes https://exercises.lol/videos/ap_physics_1/force-and-translational-dynamics2026-09-05https://exercises.lol/video-media/ap_physics_1/force-and-translational-dynamics/force-and-translational-dynamics.thumb.jpg?v=1788584514Force & Translational DynamicsThree skydivers, far above the ground. Gravity is pulling every one of them down, hard. Yet they hang there, steady, side by side. So why has that pull stopped…https://exercises.lol/video-media/ap_physics_1/force-and-translational-dynamics/force-and-translational-dynamics.enzh.mp4?v=17885845146492026-08-15yes https://exercises.lol/videos/ap_physics_1/work-energy-and-power2026-09-05https://exercises.lol/video-media/ap_physics_1/work-energy-and-power/work-energy-and-power.thumb.jpg?v=1788584519Work, Energy, and PowerLook up at the first hill of a roller coaster. A chain drags the train to the top, then lets go. There is no engine on the train — nothing pushes it again for…https://exercises.lol/video-media/ap_physics_1/work-energy-and-power/work-energy-and-power.enzh.mp4?v=17885845194872026-08-15yes https://exercises.lol/videos/ap_physics_1/linear-momentum2026-09-05https://exercises.lol/video-media/ap_physics_1/linear-momentum/linear-momentum.thumb.jpg?v=1788583926Linear MomentumFive steel balls hang in a row, just touching. Lift one, let it go, and one ball flies off the far end. Only one. Lift two, and exactly two fly off. Something…https://exercises.lol/video-media/ap_physics_1/linear-momentum/linear-momentum.enzh.mp4?v=17885839264692026-08-15yes https://exercises.lol/videos/ap_physics_1/torque-and-rotational-dynamics2026-09-05https://exercises.lol/video-media/ap_physics_1/torque-and-rotational-dynamics/torque-and-rotational-dynamics.thumb.jpg?v=1788583866Torque and Rotational DynamicsPush a heavy door right next to its hinge, as hard as you can. It barely moves. Now push with the same force, out at the handle — and it swings wide open. Same…https://exercises.lol/video-media/ap_physics_1/torque-and-rotational-dynamics/torque-and-rotational-dynamics.enzh.mp4?v=17885838664612026-08-15yes https://exercises.lol/videos/ap_physics_1/energy-and-momentum-of2026-09-05https://exercises.lol/video-media/ap_physics_1/energy-and-momentum-of/energy-and-momentum-of.thumb.jpg?v=1788584432Energy and Momentum of Rotating SystemsWatch a skater spinning with her arms stretched out. She pulls them in — and suddenly she spins much faster. Nobody pushed her. No motor started. So where did…https://exercises.lol/video-media/ap_physics_1/energy-and-momentum-of/energy-and-momentum-of.enzh.mp4?v=17885844324742026-08-15yes https://exercises.lol/videos/ap_physics_1/oscillations2026-09-03https://exercises.lol/video-media/ap_physics_1/oscillations/oscillations.thumb.jpg?v=1788428229OscillationsTwo identical springs, two identical masses. Pull one of them far down. Pull the other only a little. Let go of both at the same moment. Which one gets back…https://exercises.lol/video-media/ap_physics_1/oscillations/oscillations.enzh.mp4?v=17884282294682026-08-15yes https://exercises.lol/videos/ap_physics_1/fluids2026-09-05https://exercises.lol/video-media/ap_physics_1/fluids/fluids.thumb.jpg?v=1788584459FluidsA steel nail dropped into water goes straight to the bottom. Now look at this ship. It is built from the same steel, tens of thousands of tonnes of it, and it…https://exercises.lol/video-media/ap_physics_1/fluids/fluids.enzh.mp4?v=17885844594862026-08-15yes https://exercises.lol/videos/ap_physics_2/thermodynamics2026-09-05https://exercises.lol/video-media/ap_physics_2/thermodynamics/thermodynamics.thumb.jpg?v=1788587978ThermodynamicsPut a hot cup of coffee on a table. It always cools down. It never warms back up by taking heat out of the cool room. Both directions would balance the energy…https://exercises.lol/video-media/ap_physics_2/thermodynamics/thermodynamics.enzh.mp4?v=17885879785362026-08-15yes https://exercises.lol/videos/ap_physics_2/electric-force-field-potential2026-09-05https://exercises.lol/video-media/ap_physics_2/electric-force-field-potential/electric-force-field-potential.thumb.jpg?v=1788587776Electric Force, Field, and PotentialA thundercloud is a charge factory. Ice crystals crash inside it, and electrons collect at the bottom of the cloud. The ground below turns positive. Nothing…https://exercises.lol/video-media/ap_physics_2/electric-force-field-potential/electric-force-field-potential.enzh.mp4?v=17885877764842026-08-15yes https://exercises.lol/videos/ap_physics_2/electric-circuits2026-09-05https://exercises.lol/video-media/ap_physics_2/electric-circuits/electric-circuits.thumb.jpg?v=1788587668Electric CircuitsYou flip a switch, and the light comes on at once. So the electrons must be racing down the wire. They are not. Inside copper, electrons crawl — less than a…https://exercises.lol/video-media/ap_physics_2/electric-circuits/electric-circuits.enzh.mp4?v=17885876684652026-08-15yes https://exercises.lol/videos/ap_physics_2/magnetism-electromagnetism2026-09-05https://exercises.lol/video-media/ap_physics_2/magnetism-electromagnetism/magnetism-electromagnetism.thumb.jpg?v=1788589332Magnetism and ElectromagnetismHigh over the Arctic, the night sky glows green. These curtains of light are not fire. They are charged particles from the Sun, arriving at a million…https://exercises.lol/video-media/ap_physics_2/magnetism-electromagnetism/magnetism-electromagnetism.enzh.mp4?v=17885893325612026-08-15yes https://exercises.lol/videos/ap_physics_2/geometric-optics2026-09-05https://exercises.lol/video-media/ap_physics_2/geometric-optics/geometric-optics.thumb.jpg?v=1788587007Geometric OpticsPut a straight pencil into a glass of water, and it looks broken. Look into the bowl of a shiny spoon, and your face is upside down. Nothing bent, and nothing…https://exercises.lol/video-media/ap_physics_2/geometric-optics/geometric-optics.enzh.mp4?v=17885870075712026-08-15yes https://exercises.lol/videos/ap_physics_2/waves-sound-physical-optics2026-09-05https://exercises.lol/video-media/ap_physics_2/waves-sound-physical-optics/waves-sound-physical-optics.thumb.jpg?v=1788586084Waves, Sound, and Physical OpticsBlow a soap bubble and look closely. The film is thinner than a hair and has no colour of its own, and the light falling on it is plain white light. Yet the…https://exercises.lol/video-media/ap_physics_2/waves-sound-physical-optics/waves-sound-physical-optics.enzh.mp4?v=17885860844702026-08-15yes https://exercises.lol/videos/ap_physics_2/modern-physics2026-09-05https://exercises.lol/video-media/ap_physics_2/modern-physics/modern-physics.thumb.jpg?v=1788588154Modern PhysicsBy nineteen hundred, physics looked finished. Then three experiments broke it. A hot glowing object gave out the wrong colours. Light falling on a metal…https://exercises.lol/video-media/ap_physics_2/modern-physics/modern-physics.enzh.mp4?v=17885881545712026-08-15yes https://exercises.lol/videos/ap_physics_c_em/charges-fields-gauss2026-09-05https://exercises.lol/video-media/ap_physics_c_em/charges-fields-gauss/charges-fields-gauss.thumb.jpg?v=1788586662Electric Charges, Fields, and Gauss's LawA lightning bolt hits a car. Inside, the people feel nothing at all. Why? The metal shell around them is a conductor. Charge races over its outside surface…https://exercises.lol/video-media/ap_physics_c_em/charges-fields-gauss/charges-fields-gauss.enzh.mp4?v=17885866625922026-08-15yes https://exercises.lol/videos/ap_physics_c_em/electric-potential2026-09-05https://exercises.lol/video-media/ap_physics_c_em/electric-potential/electric-potential.thumb.jpg?v=1788584964Electric PotentialLook at these numbers. A small battery says one point five volts. A car battery says twelve. A high-voltage transmission line carries four hundred thousand. A…https://exercises.lol/video-media/ap_physics_c_em/electric-potential/electric-potential.enzh.mp4?v=17885849644812026-08-15yes https://exercises.lol/videos/ap_physics_c_em/conductors-capacitors2026-09-05https://exercises.lol/video-media/ap_physics_c_em/conductors-capacitors/conductors-capacitors.thumb.jpg?v=1788587060Conductors and CapacitorsA plane is struck by lightning about once a year, and the people inside feel almost nothing. A car in a thunderstorm is one of the safest places to sit. Why?…https://exercises.lol/video-media/ap_physics_c_em/conductors-capacitors/conductors-capacitors.enzh.mp4?v=17885870605072026-08-15yes https://exercises.lol/videos/ap_physics_c_em/circuits2026-09-05https://exercises.lol/video-media/ap_physics_c_em/circuits/circuits.thumb.jpg?v=1788597440Electric CircuitsYou flip a switch, and the lamp lights at once. So the electrons must be racing down the wire — right? Not at all. Inside that copper wire, the carriers crawl…https://exercises.lol/video-media/ap_physics_c_em/circuits/circuits.enzh.mp4?v=17885974405222026-08-15yes https://exercises.lol/videos/ap_physics_c_em/magnetic-fields2026-09-05https://exercises.lol/video-media/ap_physics_c_em/magnetic-fields/magnetic-fields.thumb.jpg?v=1788597988Magnetic Fields and ElectromagnetismLook north on a clear winter night, far enough north, and the sky glows green. Those lights are switched on by a magnetic field. The Sun throws charged…https://exercises.lol/video-media/ap_physics_c_em/magnetic-fields/magnetic-fields.enzh.mp4?v=17885979887642026-08-15yes https://exercises.lol/videos/ap_physics_c_em/electromagnetic-induction2026-09-05https://exercises.lol/video-media/ap_physics_c_em/electromagnetic-induction/electromagnetic-induction.thumb.jpg?v=1788585195Electromagnetic InductionAlmost every watt of electricity you have ever used began the same way, with a magnet and a coil of wire moving past each other. No fuel, no burning: only…https://exercises.lol/video-media/ap_physics_c_em/electromagnetic-induction/electromagnetic-induction.enzh.mp4?v=17885851955512026-08-15yes https://exercises.lol/videos/ap_physics_c_mech/kinematics2026-09-05https://exercises.lol/video-media/ap_physics_c_mech/kinematics/kinematics.thumb.jpg?v=1788585135KinematicsA rocket lifts off. Every second, its engine burns harder, so its acceleration keeps growing. Now try to find its speed with the equations from your first…https://exercises.lol/video-media/ap_physics_c_mech/kinematics/kinematics.enzh.mp4?v=17885851354512026-08-15yes https://exercises.lol/videos/ap_physics_c_mech/force-translational-dynamics2026-09-05https://exercises.lol/video-media/ap_physics_c_mech/force-translational-dynamics/force-translational-dynamics.thumb.jpg?v=1788584325Force and Translational DynamicsA cart runs around a vertical loop. At the very top it is completely upside down, with nothing holding it up. Why does it not fall off? The answer is not some…https://exercises.lol/video-media/ap_physics_c_mech/force-translational-dynamics/force-translational-dynamics.enzh.mp4?v=17885843255462026-08-15yes https://exercises.lol/videos/ap_physics_c_mech/work-energy-power2026-09-05https://exercises.lol/video-media/ap_physics_c_mech/work-energy-power/work-energy-power.thumb.jpg?v=1788584639Work, Energy, and PowerA block slides into a spring and squashes it until it stops. How far does the spring compress? Try that with a kinematic equation. You cannot — the force grows…https://exercises.lol/video-media/ap_physics_c_mech/work-energy-power/work-energy-power.enzh.mp4?v=17885846394662026-08-15yes https://exercises.lol/videos/ap_physics_c_mech/linear-momentum2026-09-05https://exercises.lol/video-media/ap_physics_c_mech/linear-momentum/linear-momentum.thumb.jpg?v=1788600262Linear MomentumA car stops in a crash. With an airbag, the driver walks away. Without one, they do not. In both cases the momentum change is exactly the same — from full…https://exercises.lol/video-media/ap_physics_c_mech/linear-momentum/linear-momentum.enzh.mp4?v=17886002624192026-08-15yes https://exercises.lol/videos/ap_physics_c_mech/torque-rotational-dynamics2026-09-05https://exercises.lol/video-media/ap_physics_c_mech/torque-rotational-dynamics/torque-rotational-dynamics.thumb.jpg?v=1788587822Torque and Rotational DynamicsPush a door at the handle and it swings open easily. Now push just as hard, right next to the hinge. Almost nothing happens. The force was the same both times.…https://exercises.lol/video-media/ap_physics_c_mech/torque-rotational-dynamics/torque-rotational-dynamics.enzh.mp4?v=17885878224412026-08-15yes https://exercises.lol/videos/ap_physics_c_mech/energy-and-momentum-of2026-09-05https://exercises.lol/video-media/ap_physics_c_mech/energy-and-momentum-of/energy-and-momentum-of.thumb.jpg?v=1788584418Energy and Momentum of Rotating SystemsWatch a figure skater spin. Arms stretched out, she turns slowly. She pulls her arms in — and without pushing off anything, she spins much faster. Nobody…https://exercises.lol/video-media/ap_physics_c_mech/energy-and-momentum-of/energy-and-momentum-of.enzh.mp4?v=17885844184922026-08-15yes https://exercises.lol/videos/ap_physics_c_mech/oscillations2026-09-03https://exercises.lol/video-media/ap_physics_c_mech/oscillations/oscillations.thumb.jpg?v=1788442255OscillationsIn a science museum, a brass ball hangs from a very long wire. It swings all day above a marked floor, untouched. Every swing takes the same time as the last.…https://exercises.lol/video-media/ap_physics_c_mech/oscillations/oscillations.enzh.mp4?v=17884422554932026-08-15yes https://exercises.lol/videos/ap_precalculus/polynomial-rational-functions2026-09-05https://exercises.lol/video-media/ap_precalculus/polynomial-rational-functions/polynomial-rational-functions.thumb.jpg?v=1788601273Polynomial & Rational FunctionsLook at this curve. It rises, then falls, then rises again — these are its turning points. It cuts across the horizontal axis — these are the roots, where the…https://exercises.lol/video-media/ap_precalculus/polynomial-rational-functions/polynomial-rational-functions.enzh.mp4?v=178860127310342026-08-15yes https://exercises.lol/videos/ap_precalculus/exponential-logarithmic-functions2026-09-05https://exercises.lol/video-media/ap_precalculus/exponential-logarithmic-functions/exponential-logarithmic-functions.thumb.jpg?v=1788600744Exponential & Logarithmic FunctionsHere are two ways for a quantity to grow. The blue line grows steadily, adding the same amount every step. The other one is doubling — multiplying by the same…https://exercises.lol/video-media/ap_precalculus/exponential-logarithmic-functions/exponential-logarithmic-functions.enzh.mp4?v=17886007448452026-08-15yes https://exercises.lol/videos/ap_precalculus/trigonometric-polar-functions2026-09-05https://exercises.lol/video-media/ap_precalculus/trigonometric-polar-functions/trigonometric-polar-functions.thumb.jpg?v=1788601049Trigonometric & Polar FunctionsWatch a point travel around a circle at a steady rate. Its height rises, falls, and rises again, over and over. Trace that height against time, and you get a…https://exercises.lol/video-media/ap_precalculus/trigonometric-polar-functions/trigonometric-polar-functions.enzh.mp4?v=17886010494872026-08-15yes https://exercises.lol/videos/ap_precalculus/functions-involving-parameters-vectors2026-09-05https://exercises.lol/video-media/ap_precalculus/functions-involving-parameters-vectors/functions-involving-parameters-vectors.thumb.jpg?v=1788600885Functions Involving Parameters, Vectors, and MatricesLook at this roller coaster. At every moment the car has two facts: where it is, and which way it is going. One equation cannot hold both. This planet runs a…https://exercises.lol/video-media/ap_precalculus/functions-involving-parameters-vectors/functions-involving-parameters-vectors.enzh.mp4?v=17886008854832026-08-15yes https://exercises.lol/videos/ap_psychology/biological-bases-of-behavior2026-09-05https://exercises.lol/video-media/ap_psychology/biological-bases-of-behavior/biological-bases-of-behavior.thumb.jpg?v=1788590204Biological Bases of BehaviorThe teacher hands out the exam paper. Before you have read a single word, your heart is already faster and your hands are cold. You did not choose that.…https://exercises.lol/video-media/ap_psychology/biological-bases-of-behavior/biological-bases-of-behavior.enzh.mp4?v=178859020410972026-09-03yes https://exercises.lol/videos/ap_psychology/cognition2026-09-05https://exercises.lol/video-media/ap_psychology/cognition/cognition.thumb.jpg?v=1788586274CognitionLook at a sentence with a letter missing and you read it anyway. Nobody had to tell you what the letter was. Your brain supplied it, instantly, without asking…https://exercises.lol/video-media/ap_psychology/cognition/cognition.enzh.mp4?v=178858627410742026-09-03yes https://exercises.lol/videos/ap_psychology/development-and-learning2026-09-05https://exercises.lol/video-media/ap_psychology/development-and-learning/development-and-learning.thumb.jpg?v=1788586747Development and LearningA four-year-old picks up a heavy glass marble and tries to bounce it on the floor. He is not being silly. He had a rule for round things: round things bounce.…https://exercises.lol/video-media/ap_psychology/development-and-learning/development-and-learning.enzh.mp4?v=17885867477382026-09-03yes https://exercises.lol/videos/ap_psychology/social-psychology-and-personality2026-09-05https://exercises.lol/video-media/ap_psychology/social-psychology-and-personality/social-psychology-and-personality.thumb.jpg?v=1788586144Social Psychology and PersonalityA driver cuts in front of you and you decide they are rude. Later you cut in front of someone, and you know exactly why: you were late, and the other lane was…https://exercises.lol/video-media/ap_psychology/social-psychology-and-personality/social-psychology-and-personality.enzh.mp4?v=17885861446242026-09-03yes https://exercises.lol/videos/ap_psychology/mental-and-physical-health2026-09-05https://exercises.lol/video-media/ap_psychology/mental-and-physical-health/mental-and-physical-health.thumb.jpg?v=1788590162Mental and Physical HealthOne person collects bus tickets and can name every route in the city. Another cannot leave the house to go to work. Only one of those is a disorder, and it is…https://exercises.lol/video-media/ap_psychology/mental-and-physical-health/mental-and-physical-health.enzh.mp4?v=17885901625572026-09-03yes https://exercises.lol/videos/ap_statistics/one-variable-data2026-09-05https://exercises.lol/video-media/ap_statistics/one-variable-data/one-variable-data.thumb.jpg?v=1788581473Exploring One-Variable DataMeasure the same thing twenty times and you will not get the same answer twenty times. Twenty students measure the same table. The values vary. That is not a…https://exercises.lol/video-media/ap_statistics/one-variable-data/one-variable-data.enzh.mp4?v=17885814735432026-08-15yes https://exercises.lol/videos/ap_statistics/collecting-data2026-09-05https://exercises.lol/video-media/ap_statistics/collecting-data/collecting-data.thumb.jpg?v=1788581307Collecting DataAn online poll collects thirty thousand replies. A careful survey asks only one thousand people. Which is closer to the truth? The small one, almost every…https://exercises.lol/video-media/ap_statistics/collecting-data/collecting-data.enzh.mp4?v=17885813074502026-08-15yes https://exercises.lol/videos/ap_statistics/probability-random-variables-and2026-09-05https://exercises.lol/video-media/ap_statistics/probability-random-variables-and/probability-random-variables-and.thumb.jpg?v=1788581541Probability, Random Variables, and Probability DistributionsA basketball player makes five shots in a row. The crowd is sure she is hot tonight. But watch what chance alone can do. Flip a fair coin twenty times. There…https://exercises.lol/video-media/ap_statistics/probability-random-variables-and/probability-random-variables-and.enzh.mp4?v=17885815415192026-08-15yes https://exercises.lol/videos/ap_statistics/sampling-distributions2026-09-05https://exercises.lol/video-media/ap_statistics/sampling-distributions/sampling-distributions.thumb.jpg?v=1788581622Sampling DistributionsTwo thousand students go to this school, and some of them cycle here. We want to know what share. Nobody can ask all two thousand, so we ask a random hundred.…https://exercises.lol/video-media/ap_statistics/sampling-distributions/sampling-distributions.enzh.mp4?v=17885816224522026-08-15yes https://exercises.lol/videos/ap_statistics/inference-for-categorical-data2026-09-05https://exercises.lol/video-media/ap_statistics/inference-for-categorical-data/inference-for-categorical-data.thumb.jpg?v=1788585724Inference for Categorical Data: ProportionsA city wants to know how many people support a new policy. We cannot ask everyone, so we ask two hundred at random. A hundred and twenty say yes — sixty…https://exercises.lol/video-media/ap_statistics/inference-for-categorical-data/inference-for-categorical-data.enzh.mp4?v=17885857244722026-08-15yes https://exercises.lol/videos/ap_statistics/inference-for-quantitative-data2026-09-05https://exercises.lol/video-media/ap_statistics/inference-for-quantitative-data/inference-for-quantitative-data.thumb.jpg?v=1788579954Inference for Quantitative Data: MeansYou already know the heart of inference. Take a sample, find its mean, then do it again and again. Even when the population is lopsided, those sample means…https://exercises.lol/video-media/ap_statistics/inference-for-quantitative-data/inference-for-quantitative-data.enzh.mp4?v=17885799544572026-08-15yes https://exercises.lol/videos/ap_statistics/inference-for-quantitative-data-slopes-92026-09-05https://exercises.lol/video-media/ap_statistics/inference-for-quantitative-data-slopes-9/inference-for-quantitative-data-slopes-9.thumb.jpg?v=1788581389Inference for Quantitative Data: SlopesHere is one class on a scatterplot: hours of revision along the bottom, test score up the side. The line of best fit climbs. But this is only one class. Take a…https://exercises.lol/video-media/ap_statistics/inference-for-quantitative-data-slopes-9/inference-for-quantitative-data-slopes-9.enzh.mp4?v=17885813894792026-08-15yes https://exercises.lol/videos/ap_us_history/period-1-1491-16072026-09-05https://exercises.lol/video-media/ap_us_history/period-1-1491-1607/period-1-1491-1607.thumb.jpg?v=1788582501Period 1: 1491 to 1607In 1491 North America was not empty and it was not one place. It held hundreds of societies, farming, hunting, fishing and trading, and they differed from each…https://exercises.lol/video-media/ap_us_history/period-1-1491-1607/period-1-1491-1607.enzh.mp4?v=17885825014662026-09-03yes https://exercises.lol/videos/ap_us_history/period-2-1607-17542026-09-05https://exercises.lol/video-media/ap_us_history/period-2-1607-1754/period-2-1607-1754.thumb.jpg?v=1788582621Period 2: 1607 to 1754Two English colonies, founded within twenty years of each other by people from the same country under the same crown. One grows tobacco with enslaved labour on…https://exercises.lol/video-media/ap_us_history/period-2-1607-1754/period-2-1607-1754.enzh.mp4?v=17885826215062026-09-03yes https://exercises.lol/videos/ap_us_history/period-3-1754-18002026-09-05https://exercises.lol/video-media/ap_us_history/period-3-1754-1800/period-3-1754-1800.thumb.jpg?v=1788582393Period 3: 1754 to 1800Britain wins the war, takes half a continent, and destroys its main rival in North America. Twelve years later its colonies are in open rebellion. Those two…https://exercises.lol/video-media/ap_us_history/period-3-1754-1800/period-3-1754-1800.enzh.mp4?v=17885823935472026-09-03yes https://exercises.lol/videos/ap_us_history/period-4-1800-18482026-09-05https://exercises.lol/video-media/ap_us_history/period-4-1800-1848/period-4-1800-1848.thumb.jpg?v=1788582484Period 4: 1800 to 1848In 1825 a canal opens, and a bag of wheat that took three weeks to reach a city now takes eight days at a tenth of the cost. Everything follows from that.…https://exercises.lol/video-media/ap_us_history/period-4-1800-1848/period-4-1800-1848.enzh.mp4?v=17885824845382026-09-03yes https://exercises.lol/videos/ap_us_history/period-5-1844-18772026-09-05https://exercises.lol/video-media/ap_us_history/period-5-1844-1877/period-5-1844-1877.thumb.jpg?v=1788582666Period 5: 1844 to 1877In one decade a country doubles its territory. That sounds like a triumph and it brings one question with it: will slavery go there? Every compromise from then…https://exercises.lol/video-media/ap_us_history/period-5-1844-1877/period-5-1844-1877.enzh.mp4?v=17885826664532026-09-03yes https://exercises.lol/videos/ap_us_history/period-6-1865-18982026-09-03https://exercises.lol/video-media/ap_us_history/period-6-1865-1898/period-6-1865-1898.thumb.jpg?v=1788445969Period 6: 1865 to 1898Here is the puzzle at the centre of this period. An American farmer in 1890 grew more wheat than his father ever had, with better machines, on more land…https://exercises.lol/video-media/ap_us_history/period-6-1865-1898/period-6-1865-1898.enzh.mp4?v=17884459694362026-09-03yes https://exercises.lol/videos/ap_us_history/period-7-1890-19452026-09-05https://exercises.lol/video-media/ap_us_history/period-7-1890-1945/period-7-1890-1945.thumb.jpg?v=1788582658Period 7: 1890 to 1945This is the longest period on the course and the densest, and students drown in it because they try to remember it as one story. It is three. Federal power…https://exercises.lol/video-media/ap_us_history/period-7-1890-1945/period-7-1890-1945.enzh.mp4?v=17885826584602026-09-03yes https://exercises.lol/videos/ap_us_history/period-8-1945-19802026-09-05https://exercises.lol/video-media/ap_us_history/period-8-1945-1980/period-8-1945-1980.thumb.jpg?v=1788595882Period 8: 1945 to 1980Two arguments dominate this period, and they look unrelated until you see what they share. How far should the United States go to contain communism abroad? And…https://exercises.lol/video-media/ap_us_history/period-8-1945-1980/period-8-1945-1980.enzh.mp4?v=17885958824062026-09-03yes https://exercises.lol/videos/ap_us_history/period-9-1980-present2026-09-05https://exercises.lol/video-media/ap_us_history/period-9-1980-present/period-9-1980-present.thumb.jpg?v=1788595722Period 9: 1980 to the presentThis period is short in topics and wide in scope, and the exam treats it as the culmination of the whole course. Three arguments that have run since the…https://exercises.lol/video-media/ap_us_history/period-9-1980-present/period-9-1980-present.enzh.mp4?v=17885957223452026-09-03yes https://exercises.lol/videos/ap_world_history/unit-1-the-global-tapestry2026-09-03https://exercises.lol/video-media/ap_world_history/unit-1-the-global-tapestry/unit-1-the-global-tapestry.thumb.jpg?v=1788450971Unit 1: The Global TapestryUnit 1 asks you to hold six regions of the world in your head at once, and students try to do it by memorising six separate stories. That is why the unit feels…https://exercises.lol/video-media/ap_world_history/unit-1-the-global-tapestry/unit-1-the-global-tapestry.enzh.mp4?v=17884509714112026-09-03yes https://exercises.lol/videos/ap_world_history/unit-2-networks-of-exchange2026-09-03https://exercises.lol/video-media/ap_world_history/unit-2-networks-of-exchange/unit-2-networks-of-exchange.thumb.jpg?v=1788457999Unit 2: Networks of ExchangeSilk, porcelain, spices, gold, salt. Students spend hours learning who traded what, and then a question asks why trade grew and the list is no help at all.…https://exercises.lol/video-media/ap_world_history/unit-2-networks-of-exchange/unit-2-networks-of-exchange.enzh.mp4?v=17884579994102026-09-03yes https://exercises.lol/videos/ap_world_history/unit-3-land-based-empires2026-09-05https://exercises.lol/video-media/ap_world_history/unit-3-land-based-empires/unit-3-land-based-empires.thumb.jpg?v=1788579262Unit 3: Land-Based EmpiresEvery ruler in this unit faces the same practical problem. You have conquered territory that is weeks of travel from your capital, and the people who actually…https://exercises.lol/video-media/ap_world_history/unit-3-land-based-empires/unit-3-land-based-empires.enzh.mp4?v=17885792623342026-09-03yes https://exercises.lol/videos/ap_world_history/unit-4-transoceanic-interconnections2026-09-05https://exercises.lol/video-media/ap_world_history/unit-4-transoceanic-interconnections/unit-4-transoceanic-interconnections.thumb.jpg?v=1788579521Unit 4: Transoceanic InterconnectionsAsk most students why Europeans sailed and you get a name — Columbus, da Gama, Magellan. The explorer is the least useful answer available. What actually made…https://exercises.lol/video-media/ap_world_history/unit-4-transoceanic-interconnections/unit-4-transoceanic-interconnections.enzh.mp4?v=17885795213972026-09-03yes https://exercises.lol/videos/ap_world_history/unit-5-revolutions2026-09-03https://exercises.lol/video-media/ap_world_history/unit-5-revolutions/unit-5-revolutions.thumb.jpg?v=1788454549Unit 5: RevolutionsThis unit has two engines running at once. An intellectual revolution that changed how people justified political authority, and an industrial revolution that…https://exercises.lol/video-media/ap_world_history/unit-5-revolutions/unit-5-revolutions.enzh.mp4?v=17884545494052026-09-03yes https://exercises.lol/videos/ap_world_history/unit-6-consequences-of-industrialization2026-09-05https://exercises.lol/video-media/ap_world_history/unit-6-consequences-of-industrialization/unit-6-consequences-of-industrialization.thumb.jpg?v=1788579519Unit 6: Consequences of IndustrializationThis is the unit on the consequences of industrialisation, 1750 to 1900. One distinction decides most of the marks in this unit, and it is easy to state and…https://exercises.lol/video-media/ap_world_history/unit-6-consequences-of-industrialization/unit-6-consequences-of-industrialization.enzh.mp4?v=17885795193742026-09-03yes https://exercises.lol/videos/ap_world_history/unit-7-global-conflict2026-09-05https://exercises.lol/video-media/ap_world_history/unit-7-global-conflict/unit-7-global-conflict.thumb.jpg?v=1788576319Unit 7: Global ConflictThe organising question of this unit is not what happened in the wars. Campaigns and battles earn almost nothing on this exam. The question is why the…https://exercises.lol/video-media/ap_world_history/unit-7-global-conflict/unit-7-global-conflict.enzh.mp4?v=17885763195122026-09-03yes https://exercises.lol/videos/ap_world_history/unit-8-cold-war-and-decolonization2026-09-05https://exercises.lol/video-media/ap_world_history/unit-8-cold-war-and-decolonization/unit-8-cold-war-and-decolonization.thumb.jpg?v=1788575152Unit 8: Cold War and DecolonizationTwo processes run through this unit at the same time: a global ideological rivalry, and the end of empire. Studied separately they are twice the work and half…https://exercises.lol/video-media/ap_world_history/unit-8-cold-war-and-decolonization/unit-8-cold-war-and-decolonization.enzh.mp4?v=17885751525202026-09-03yes https://exercises.lol/videos/ap_world_history/unit-9-globalization2026-09-05https://exercises.lol/video-media/ap_world_history/unit-9-globalization/unit-9-globalization.thumb.jpg?v=1788579538Unit 9: GlobalizationUnit 9's central move is evaluative rather than narrative. Almost every development it names produced a benefit and a cost, and the questions reward answers…https://exercises.lol/video-media/ap_world_history/unit-9-globalization/unit-9-globalization.enzh.mp4?v=17885795384582026-09-03yes https://exercises.lol/videos/code_a_level_cs/nested-loops2026-09-05https://exercises.lol/video-media/code_a_level_cs/nested-loops/nested-loops.thumb.jpg?v=1788615732Nested loopsOne loop inside another sounds simple, and one sentence about it gets misread every year: for every single pass of the outer loop, the inner loop runs all…https://exercises.lol/video-media/code_a_level_cs/nested-loops/nested-loops.enzh.mp4?v=17886157321262026-08-23yes https://exercises.lol/videos/code_a_level_cs/files2026-09-05https://exercises.lol/video-media/code_a_level_cs/files/files.thumb.jpg?v=1788615716Text filesOpening a file takes a mode, and the mode is not a formality. Read gives you what is there. Write throws away what was there and starts a fresh file. Append…https://exercises.lol/video-media/code_a_level_cs/files/files.enzh.mp4?v=17886157161222026-08-23yes https://exercises.lol/videos/code_a_level_cs/exceptions2026-09-05https://exercises.lol/video-media/code_a_level_cs/exceptions/exceptions.thumb.jpg?v=1788615747ExceptionsAsk Python to turn the word hello into a number and it raises an exception — a value error. And an exception that nobody handles stops the program on the spot…https://exercises.lol/video-media/code_a_level_cs/exceptions/exceptions.enzh.mp4?v=17886157471252026-08-23yes https://exercises.lol/videos/code_a_level_cs/stacks2026-09-05https://exercises.lol/video-media/code_a_level_cs/stacks/stacks.thumb.jpg?v=1788615683StacksA stack is the first abstract data type in this course, and the word abstract is doing real work. What defines a stack is its operations: push, pop, peek…https://exercises.lol/video-media/code_a_level_cs/stacks/stacks.enzh.mp4?v=17886156831302026-08-23yes https://exercises.lol/videos/code_a_level_cs/queues2026-09-05https://exercises.lol/video-media/code_a_level_cs/queues/queues.thumb.jpg?v=1788615830QueuesA queue is the other ADT, and it behaves like a line of people. A new item joins at the back. The next item out leaves from the front. Put the two structures…https://exercises.lol/video-media/code_a_level_cs/queues/queues.enzh.mp4?v=17886158301222026-08-22yes https://exercises.lol/videos/code_a_level_cs/linked-lists2026-09-05https://exercises.lol/video-media/code_a_level_cs/linked-lists/linked-lists.thumb.jpg?v=1788615683Linked listsA linked list is a chain of nodes, and each node holds two things: a piece of data, and a link to the next node. Here a node is just a dictionary with those…https://exercises.lol/video-media/code_a_level_cs/linked-lists/linked-lists.enzh.mp4?v=17886156831252026-08-23yes https://exercises.lol/videos/code_a_level_cs/searching2026-09-05https://exercises.lol/video-media/code_a_level_cs/searching/searching.thumb.jpg?v=1788615731SearchingSearching means finding whether a value is in a list, and where. Note the second half of that: what comes back is the position, not the value — the caller…https://exercises.lol/video-media/code_a_level_cs/searching/searching.enzh.mp4?v=17886157311332026-08-23yes https://exercises.lol/videos/code_a_level_cs/sorting2026-09-05https://exercises.lol/video-media/code_a_level_cs/sorting/sorting.thumb.jpg?v=1788615819SortingBubble sort only ever looks at neighbours. Walk the list and compare each pair in turn, swapping any that are the wrong way round. Watch the five: compared…https://exercises.lol/video-media/code_a_level_cs/sorting/sorting.enzh.mp4?v=17886158191212026-08-23yes https://exercises.lol/videos/code_a_level_cs/recursion2026-09-05https://exercises.lol/video-media/code_a_level_cs/recursion/recursion.thumb.jpg?v=1788615725RecursionRecursion is a function that calls itself, and every recursive function has exactly two parts. The base case is the smallest version of the problem, and it is…https://exercises.lol/video-media/code_a_level_cs/recursion/recursion.enzh.mp4?v=17886157251312026-08-23yes https://exercises.lol/videos/code_a_level_cs/classes-objects2026-09-05https://exercises.lol/video-media/code_a_level_cs/classes-objects/classes-objects.thumb.jpg?v=1788615754Classes & objectsA class defines a new kind of thing — a type you invent yourself. This one says a point has an x and a y, and that is all it says: it holds no numbers, because…https://exercises.lol/video-media/code_a_level_cs/classes-objects/classes-objects.enzh.mp4?v=17886157541582026-08-23yes https://exercises.lol/videos/code_a_level_cs/inheritance2026-09-05https://exercises.lol/video-media/code_a_level_cs/inheritance/inheritance.thumb.jpg?v=1788615767Inheritance & encapsulationInheritance lets a new class start from an existing one instead of from nothing. Animal knows how to describe itself. Now two classes built on it: Bird and…https://exercises.lol/video-media/code_a_level_cs/inheritance/inheritance.enzh.mp4?v=17886157671372026-08-23yes https://exercises.lol/videos/code_a_level_cs/paradigms2026-09-05https://exercises.lol/video-media/code_a_level_cs/paradigms/paradigms.thumb.jpg?v=1788615835Programming paradigmsA paradigm is a style of organising a program — not a language, a style. The same problem can be written in any of them. Procedural is a list of steps, grouped…https://exercises.lol/video-media/code_a_level_cs/paradigms/paradigms.enzh.mp4?v=17886158351642026-08-23yes https://exercises.lol/videos/code_a_level_cs/hash-tables2026-09-05https://exercises.lol/video-media/code_a_level_cs/hash-tables/hash-tables.thumb.jpg?v=1788615781Hash tablesA hash table is a list of slots, and the trick is that you never look for anything. You compute where it belongs. Give it the key cat and a function answers…https://exercises.lol/video-media/code_a_level_cs/hash-tables/hash-tables.enzh.mp4?v=17886157811602026-08-23yes https://exercises.lol/videos/code_a_level_cs/binary-search-trees2026-09-05https://exercises.lol/video-media/code_a_level_cs/binary-search-trees/binary-search-trees.thumb.jpg?v=1788615749Binary search treesA binary search tree keeps values sorted by where it puts them. Each node holds a value and links to up to two children, and one rule governs the lot. Take the…https://exercises.lol/video-media/code_a_level_cs/binary-search-trees/binary-search-trees.enzh.mp4?v=17886157491612026-08-23yes https://exercises.lol/videos/code_a_level_cs/graphs2026-09-05https://exercises.lol/video-media/code_a_level_cs/graphs/graphs.thumb.jpg?v=1788615832GraphsA graph is a set of nodes joined by edges. The circles are the nodes — you will also see them called vertices — and the lines are edges. That is the whole…https://exercises.lol/video-media/code_a_level_cs/graphs/graphs.enzh.mp4?v=17886158321312026-08-23yes https://exercises.lol/videos/code_ap_csa/java-basics2026-09-05https://exercises.lol/video-media/code_ap_csa/java-basics/java-basics.thumb.jpg?v=1788615935Java basicsAP Computer Science A uses Java, and Java looks intimidating on day one because of the ceremony around your code. So look at what is actually there. In the…https://exercises.lol/video-media/code_ap_csa/java-basics/java-basics.enzh.mp4?v=17886159351072026-08-23yes https://exercises.lol/videos/code_ap_csa/using-objects2026-09-05https://exercises.lol/video-media/code_ap_csa/using-objects/using-objects.thumb.jpg?v=1788616027Using objectsHere is the picture the whole lesson depends on. When you write String greeting equals Hello, the variable does not contain the letters. It holds a reference…https://exercises.lol/video-media/code_ap_csa/using-objects/using-objects.enzh.mp4?v=17886160271402026-08-23yes https://exercises.lol/videos/code_ap_csa/selection2026-09-05https://exercises.lol/video-media/code_ap_csa/selection/selection.thumb.jpg?v=1788616011Booleans and selectionA relational operator compares two values and produces a boolean — true or false. Score greater than fifty is true. Score double-equals one hundred is false.…https://exercises.lol/video-media/code_ap_csa/selection/selection.enzh.mp4?v=17886160111142026-08-23yes https://exercises.lol/videos/code_ap_csa/loops2026-09-05https://exercises.lol/video-media/code_ap_csa/loops/loops.thumb.jpg?v=1788615936Loops in JavaEvery loop, in every language, needs the same three parts, and a while loop spreads them out where you can see them. A start: i is set to one, before the loop.…https://exercises.lol/video-media/code_ap_csa/loops/loops.enzh.mp4?v=17886159361112026-08-23yes https://exercises.lol/videos/code_ap_csa/strings-loops2026-09-05https://exercises.lol/video-media/code_ap_csa/strings-loops/strings-loops.thumb.jpg?v=1788616052Strings and nested loopsTo go through a String you loop over its indexes and read one character at a time with charAt. Watch the index move along. Now look at the test carefully: i…https://exercises.lol/video-media/code_ap_csa/strings-loops/strings-loops.enzh.mp4?v=17886160521042026-08-23yes https://exercises.lol/videos/code_ap_csa/writing-a-class2026-09-05https://exercises.lol/video-media/code_ap_csa/writing-a-class/writing-a-class.thumb.jpg?v=1788616022Writing a classUntil now you have used other people's types. Now you make your own. A class is a blueprint: it says what a Dog HAS — a name and an age. Those are its instance…https://exercises.lol/video-media/code_ap_csa/writing-a-class/writing-a-class.enzh.mp4?v=17886160221212026-08-23yes https://exercises.lol/videos/code_ap_csa/encapsulation2026-09-05https://exercises.lol/video-media/code_ap_csa/encapsulation/encapsulation.thumb.jpg?v=1788616026EncapsulationEncapsulation means hiding an object's data and only changing it through methods. Mark a field private and outside code cannot touch it — the direct route is…https://exercises.lol/video-media/code_ap_csa/encapsulation/encapsulation.enzh.mp4?v=17886160261132026-08-23yes https://exercises.lol/videos/code_ap_csa/arrays2026-09-05https://exercises.lol/video-media/code_ap_csa/arrays/arrays.thumb.jpg?v=1788615934ArraysAn array holds many values of one type under one name. Each value sits at an index, and indexes start at zero. So with three scores, scores zero is ninety and…https://exercises.lol/video-media/code_ap_csa/arrays/arrays.enzh.mp4?v=17886159341022026-08-23yes https://exercises.lol/videos/code_ap_csa/array-algorithms2026-09-05https://exercises.lol/video-media/code_ap_csa/array-algorithms/array-algorithms.thumb.jpg?v=1788615908Array algorithmsFour array jobs turn up on nearly every paper, and they are all the same shape. Sum: start at zero and add every value. Count: start at zero and add one, but…https://exercises.lol/video-media/code_ap_csa/array-algorithms/array-algorithms.enzh.mp4?v=17886159081282026-08-23yes https://exercises.lol/videos/code_ap_csa/arraylist2026-09-05https://exercises.lol/video-media/code_ap_csa/arraylist/arraylist.thumb.jpg?v=1788616023ArrayListAn array's length is frozen the moment you make it, and often you do not know how many things there will be. That is what ArrayList is for. Watch: names dot…https://exercises.lol/video-media/code_ap_csa/arraylist/arraylist.enzh.mp4?v=17886160231232026-08-23yes https://exercises.lol/videos/code_ap_csa/arraylist-algorithms2026-09-05https://exercises.lol/video-media/code_ap_csa/arraylist-algorithms/arraylist-algorithms.thumb.jpg?v=1788615961The remove bugThe safe way to keep only some items is not to remove the others — it is to build a second list. Walk the original, test each value, and the loop copies the…https://exercises.lol/video-media/code_ap_csa/arraylist-algorithms/arraylist-algorithms.enzh.mp4?v=17886159611132026-08-23yes https://exercises.lol/videos/code_ap_csa/two-d-arrays2026-09-05https://exercises.lol/video-media/code_ap_csa/two-d-arrays/two-d-arrays.thumb.jpg?v=17886160422-D arraysA 2-D array is a grid — really, an array whose items are themselves arrays, one per row. To reach a cell you give two indexes, and the order is fixed: row…https://exercises.lol/video-media/code_ap_csa/two-d-arrays/two-d-arrays.enzh.mp4?v=17886160421012026-08-23yes https://exercises.lol/videos/code_ap_csa/searching2026-09-05https://exercises.lol/video-media/code_ap_csa/searching/searching.thumb.jpg?v=1788615992SearchingLinear search checks the items one after another from the start. Watch the counter climb: one look, two, three, and it keeps going until it lands on…https://exercises.lol/video-media/code_ap_csa/searching/searching.enzh.mp4?v=17886159921012026-08-23yes https://exercises.lol/videos/code_ap_csa/sorting2026-09-05https://exercises.lol/video-media/code_ap_csa/sorting/sorting.thumb.jpg?v=1788615888SortingSelection sort works by finding the smallest value in the unsorted part and swapping it to the front. Start with seven, three, nine, two, five. Smallest is…https://exercises.lol/video-media/code_ap_csa/sorting/sorting.enzh.mp4?v=17886158881152026-08-23yes https://exercises.lol/videos/code_ap_csa/recursion2026-09-05https://exercises.lol/video-media/code_ap_csa/recursion/recursion.thumb.jpg?v=1788615980RecursionA recursive method is one that calls itself, and every single one has exactly two parts. The base case is the question it can answer directly, with no further…https://exercises.lol/video-media/code_ap_csa/recursion/recursion.enzh.mp4?v=17886159801222026-08-23yes https://exercises.lol/videos/code_ap_csa/files2026-09-05https://exercises.lol/video-media/code_ap_csa/files/files.thumb.jpg?v=1788615940Text filesPrintWriter writes to a file with the same println you already know. But there is one line people forget, and it costs everything. Leave out close and nothing…https://exercises.lol/video-media/code_ap_csa/files/files.enzh.mp4?v=1788615940982026-08-23yes https://exercises.lol/videos/code_ap_csa/inheritance2026-09-05https://exercises.lol/video-media/code_ap_csa/inheritance/inheritance.thumb.jpg?v=1788616019InheritanceInheritance lets one class build on another instead of copying it. Animal has a name and a speak method; Dog and Cat extend Animal, so they get both for free…https://exercises.lol/video-media/code_ap_csa/inheritance/inheritance.enzh.mp4?v=17886160191192026-08-23yes https://exercises.lol/videos/code_ap_csa/polymorphism2026-09-05https://exercises.lol/video-media/code_ap_csa/polymorphism/polymorphism.thumb.jpg?v=1788615920PolymorphismHere is the idea, and it is worth watching rather than reading. The variable is declared as an Animal, and it points at a Dog. Call a dot speak and you get…https://exercises.lol/video-media/code_ap_csa/polymorphism/polymorphism.enzh.mp4?v=17886159201042026-08-23yes https://exercises.lol/videos/code_ap_csa/frq-workshop2026-09-05https://exercises.lol/video-media/code_ap_csa/frq-workshop/frq-workshop.thumb.jpg?v=1788615935The four FRQ typesThe free-response section is four questions, and every year they are the same four shapes. Question one asks you to write a method from a description — that is…https://exercises.lol/video-media/code_ap_csa/frq-workshop/frq-workshop.enzh.mp4?v=17886159351062026-08-23yes https://exercises.lol/videos/code_ap_csp/what-computing-is2026-09-05https://exercises.lol/video-media/code_ap_csp/what-computing-is/what-computing-is.thumb.jpg?v=1788616234What computing isA program is a set of instructions a computer follows, and almost every one of them has this shape. Input: data goes in — a number you type, a tap, a file.…https://exercises.lol/video-media/code_ap_csp/what-computing-is/what-computing-is.enzh.mp4?v=17886162341272026-08-23yes https://exercises.lol/videos/code_ap_csp/bits-and-binary2026-09-05https://exercises.lol/video-media/code_ap_csp/bits-and-binary/bits-and-binary.thumb.jpg?v=1788616116Bits and binaryA bit is one digit that is either zero or one, and computers store everything — numbers, text, pictures, music — as bits. The reason is physical. A chip is…https://exercises.lol/video-media/code_ap_csp/bits-and-binary/bits-and-binary.enzh.mp4?v=17886161161412026-08-23yes https://exercises.lol/videos/code_ap_csp/compression2026-09-05https://exercises.lol/video-media/code_ap_csp/compression/compression.thumb.jpg?v=1788616159Data compressionData costs space to store and time to send, so we compress it — and there are two kinds. Lossless makes a file smaller while keeping every single bit. Follow…https://exercises.lol/video-media/code_ap_csp/compression/compression.enzh.mp4?v=17886161591042026-08-23yes https://exercises.lol/videos/code_ap_csp/variables2026-09-05https://exercises.lol/video-media/code_ap_csp/variables/variables.thumb.jpg?v=1788616163Variables and expressionsA variable stores a value so you can use it later, and the equals sign does not mean equals — it means "store into". Which is why the second line here confuses…https://exercises.lol/video-media/code_ap_csp/variables/variables.enzh.mp4?v=17886161631302026-08-23yes https://exercises.lol/videos/code_ap_csp/lists2026-09-05https://exercises.lol/video-media/code_ap_csp/lists/lists.thumb.jpg?v=1788616166Lists and data abstractionA program often needs many values at once — a whole class of scores. One variable per value gets messy fast, and it does not scale at all. A list holds many…https://exercises.lol/video-media/code_ap_csp/lists/lists.enzh.mp4?v=17886161661272026-08-23yes https://exercises.lol/videos/code_ap_csp/selection2026-09-05https://exercises.lol/video-media/code_ap_csp/selection/selection.thumb.jpg?v=1788616156SelectionSelection means the program picks what to do based on a condition. And an if-elif-else is a chain, not three separate questions — watch what happens with the…https://exercises.lol/video-media/code_ap_csp/selection/selection.enzh.mp4?v=17886161561292026-08-23yes https://exercises.lol/videos/code_ap_csp/iteration2026-09-05https://exercises.lol/video-media/code_ap_csp/iteration/iteration.thumb.jpg?v=1788616204IterationIteration means doing the same steps again and again, which is how a little code does a lot of work. The commonest loop counts with range. And here is the…https://exercises.lol/video-media/code_ap_csp/iteration/iteration.enzh.mp4?v=17886162041302026-08-23yes https://exercises.lol/videos/code_ap_csp/procedures2026-09-05https://exercises.lol/video-media/code_ap_csp/procedures/procedures.thumb.jpg?v=1788616241Procedures and abstractionA procedure is a named block of code you can use again and again. In Python you make one with def, then a name, then brackets, and the code goes indented…https://exercises.lol/video-media/code_ap_csp/procedures/procedures.enzh.mp4?v=17886162411092026-08-23yes https://exercises.lol/videos/code_ap_csp/searching2026-09-05https://exercises.lol/video-media/code_ap_csp/searching/searching.thumb.jpg?v=1788616200Algorithms: searchingAn algorithm is a clear, finite list of steps that solves a problem, and searching is the classic one: find where a value sits in a list. Linear search checks…https://exercises.lol/video-media/code_ap_csp/searching/searching.enzh.mp4?v=17886162001282026-08-23yes https://exercises.lol/videos/code_ap_csp/randomness2026-09-05https://exercises.lol/video-media/code_ap_csp/randomness/randomness.thumb.jpg?v=1788616121Randomness and simulationSome programs need chance — games, experiments, models of the real world. The random tools live in a module, so you write import random at the top. Then…https://exercises.lol/video-media/code_ap_csp/randomness/randomness.enzh.mp4?v=17886161211222026-08-23yes https://exercises.lol/videos/code_ap_csp/efficiency2026-09-05https://exercises.lol/video-media/code_ap_csp/efficiency/efficiency.thumb.jpg?v=1788616253Algorithmic efficiencyTwo programs can both be correct and still take wildly different amounts of time, so we need a way to compare them. We measure an algorithm by how many steps…https://exercises.lol/video-media/code_ap_csp/efficiency/efficiency.enzh.mp4?v=17886162531152026-08-23yes https://exercises.lol/videos/code_ap_csp/internet2026-09-05https://exercises.lol/video-media/code_ap_csp/internet/internet.thumb.jpg?v=1788616245The Internet and how data travelsThe Internet is an enormous network of computers joined together, and no single one of them is in charge. When you send something across it, the data does not…https://exercises.lol/video-media/code_ap_csp/internet/internet.enzh.mp4?v=17886162451352026-08-23yes https://exercises.lol/videos/code_ap_csp/parallel2026-09-05https://exercises.lol/video-media/code_ap_csp/parallel/parallel.thumb.jpg?v=1788616171Parallel and distributed computingMost simple programs are sequential: step one finishes before step two starts. Easy to follow, but slow for a big job — look at how far that top row runs.…https://exercises.lol/video-media/code_ap_csp/parallel/parallel.enzh.mp4?v=17886161711312026-08-23yes https://exercises.lol/videos/code_ap_csp/impact2026-09-05https://exercises.lol/video-media/code_ap_csp/impact/impact.thumb.jpg?v=1788616177Impact of computingComputing touches almost every part of life, and the same tool brings benefits and harms — not one or the other, both at once. Social media lets you stay in…https://exercises.lol/video-media/code_ap_csp/impact/impact.enzh.mp4?v=17886161771422026-08-23yes https://exercises.lol/videos/code_ap_csp/create-task2026-09-05https://exercises.lol/video-media/code_ap_csp/create-task/create-task.thumb.jpg?v=1788616252The Create Performance TaskThe Create Performance Task is a small program you design and build yourself, and it has a short list of requirements. A list, or another collection, that…https://exercises.lol/video-media/code_ap_csp/create-task/create-task.enzh.mp4?v=17886162521332026-08-23yes https://exercises.lol/videos/code_c_basics/c-skeleton2026-09-05https://exercises.lol/video-media/code_c_basics/c-skeleton/c-skeleton.thumb.jpg?v=1788616549The C skeletonC works differently from the languages elsewhere on this site, and the difference shapes everything else. You write the source file. Then a compiler reads the…https://exercises.lol/video-media/code_c_basics/c-skeleton/c-skeleton.enzh.mp4?v=17886165491492026-08-22yes https://exercises.lol/videos/code_c_basics/types-arithmetic2026-09-05https://exercises.lol/video-media/code_c_basics/types-arithmetic/types-arithmetic.thumb.jpg?v=1788616380Types and arithmeticIn C, every variable has a type, and you say what it is when you make it. An int holds a whole number. A double holds a decimal. A char holds a single…https://exercises.lol/video-media/code_c_basics/types-arithmetic/types-arithmetic.enzh.mp4?v=17886163801482026-08-23yes https://exercises.lol/videos/code_c_basics/selection2026-09-05https://exercises.lol/video-media/code_c_basics/selection/selection.thumb.jpg?v=1788616456Selection in CC does not have a true-or-false type the way the other languages here do. Instead it has a rule: zero is false, and everything else — one, forty-two, even…https://exercises.lol/video-media/code_c_basics/selection/selection.enzh.mp4?v=17886164561482026-08-23yes https://exercises.lol/videos/code_c_basics/loops2026-09-05https://exercises.lol/video-media/code_c_basics/loops/loops.thumb.jpg?v=1788616437Loops in CC gives you two loops, and for counting they do the same job. The while version puts the start, the test and the step in three separate places, and the day you…https://exercises.lol/video-media/code_c_basics/loops/loops.enzh.mp4?v=17886164371302026-08-22yes https://exercises.lol/videos/code_c_basics/functions2026-09-05https://exercises.lol/video-media/code_c_basics/functions/functions.thumb.jpg?v=1788616372Functions in CA C function tells you everything about itself in its first line. It starts with the return type — what comes back — and that is required; you cannot leave it…https://exercises.lol/video-media/code_c_basics/functions/functions.enzh.mp4?v=17886163721222026-08-23yes https://exercises.lol/videos/code_c_basics/nested-loops2026-09-05https://exercises.lol/video-media/code_c_basics/nested-loops/nested-loops.thumb.jpg?v=1788616520Nested loopsA loop inside a loop is not complicated, but the order matters and it is easy to get backwards. The outer counter takes one value. Then the inner loop runs all…https://exercises.lol/video-media/code_c_basics/nested-loops/nested-loops.enzh.mp4?v=17886165201132026-08-22yes https://exercises.lol/videos/code_c_basics/arrays2026-09-05https://exercises.lol/video-media/code_c_basics/arrays/arrays.thumb.jpg?v=1788616381Arrays in CAn array is several boxes of the same type under one name, sitting side by side in memory. You declare it with a size, and you reach an item with square…https://exercises.lol/video-media/code_c_basics/arrays/arrays.enzh.mp4?v=17886163811512026-08-22yes https://exercises.lol/videos/code_c_basics/pointers2026-09-05https://exercises.lol/video-media/code_c_basics/pointers/pointers.thumb.jpg?v=1788616456PointersTwo lessons ago something odd happened. A function that added one to an int changed nothing outside, because the copy was changed and then thrown away. But a…https://exercises.lol/video-media/code_c_basics/pointers/pointers.enzh.mp4?v=17886164561542026-08-22yes https://exercises.lol/videos/code_c_basics/strings2026-09-05https://exercises.lol/video-media/code_c_basics/strings/strings.thumb.jpg?v=1788616478Strings in CC has no string type at all. What it has is an array of char, and everything about strings in this language follows from that. Write the word hi and you get an…https://exercises.lol/video-media/code_c_basics/strings/strings.enzh.mp4?v=17886164781482026-08-22yes https://exercises.lol/videos/code_c_basics/array-algorithms2026-09-05https://exercises.lol/video-media/code_c_basics/array-algorithms/array-algorithms.thumb.jpg?v=1788616545Array algorithmsFour jobs come up again and again with arrays, and they look like four different recipes. They are not. Every one of them is the same loop over every item…https://exercises.lol/video-media/code_c_basics/array-algorithms/array-algorithms.enzh.mp4?v=17886165451502026-08-22yes https://exercises.lol/videos/code_c_basics/two-d-arrays2026-09-05https://exercises.lol/video-media/code_c_basics/two-d-arrays/two-d-arrays.thumb.jpg?v=1788616405Two-dimensional arraysA seating plan, a chessboard, a month of temperatures for six cities — these are grids, and one index is not enough for them. So C lets you write two. This…https://exercises.lol/video-media/code_c_basics/two-d-arrays/two-d-arrays.enzh.mp4?v=17886164051452026-08-23yes https://exercises.lol/videos/code_c_basics/searching2026-09-05https://exercises.lol/video-media/code_c_basics/searching/searching.thumb.jpg?v=1788616524SearchingYou met this one last lesson. Linear search checks the items one after another, from the front, and returns the index as soon as one matches. If the loop runs…https://exercises.lol/video-media/code_c_basics/searching/searching.enzh.mp4?v=17886165241502026-08-23yes https://exercises.lol/videos/code_c_basics/sorting2026-09-05https://exercises.lol/video-media/code_c_basics/sorting/sorting.thumb.jpg?v=1788616384SortingEvery sort in this lesson is built on one small move: exchanging two items. And you cannot do it in two lines, because a box only holds one thing. You have to…https://exercises.lol/video-media/code_c_basics/sorting/sorting.enzh.mp4?v=17886163841482026-08-23yes https://exercises.lol/videos/code_c_basics/recursion2026-09-05https://exercises.lol/video-media/code_c_basics/recursion/recursion.thumb.jpg?v=1788616325RecursionA recursive function is one that calls itself, and every single one has the same two parts. The base case: the smallest version of the problem, which you can…https://exercises.lol/video-media/code_c_basics/recursion/recursion.enzh.mp4?v=17886163251492026-08-23yes https://exercises.lol/videos/code_c_basics/structs2026-09-05https://exercises.lol/video-media/code_c_basics/structs/structs.thumb.jpg?v=1788616494StructsSome values belong together. A point is an x and a y; a rectangle is a width and a height. You can keep them in separate variables, but three points means six…https://exercises.lol/video-media/code_c_basics/structs/structs.enzh.mp4?v=17886164941432026-08-22yes https://exercises.lol/videos/code_c_basics/dynamic-memory2026-09-05https://exercises.lol/video-media/code_c_basics/dynamic-memory/dynamic-memory.thumb.jpg?v=1788616321Dynamic memoryEvery local variable you have written so far lives on the stack. It appears when the function starts and vanishes when it returns, which is usually exactly…https://exercises.lol/video-media/code_c_basics/dynamic-memory/dynamic-memory.enzh.mp4?v=17886163211452026-08-23yes https://exercises.lol/videos/code_c_basics/linked-lists2026-09-05https://exercises.lol/video-media/code_c_basics/linked-lists/linked-lists.thumb.jpg?v=1788616372Linked listsAn array is one solid block. A linked list is the opposite: small structs called nodes, scattered anywhere in the heap, each one holding a value and a pointer…https://exercises.lol/video-media/code_c_basics/linked-lists/linked-lists.enzh.mp4?v=17886163721402026-08-22yes https://exercises.lol/videos/code_c_basics/stacks-queues2026-09-05https://exercises.lol/video-media/code_c_basics/stacks-queues/stacks-queues.thumb.jpg?v=1788616562Stacks and queuesA stack and a queue both hold a line of items. They differ in one thing only: which item comes out next. Put one, two and three into a stack and it behaves…https://exercises.lol/video-media/code_c_basics/stacks-queues/stacks-queues.enzh.mp4?v=17886165621402026-08-23yes https://exercises.lol/videos/code_c_basics/text-files2026-09-05https://exercises.lol/video-media/code_c_basics/text-files/text-files.thumb.jpg?v=1788616416Text filesEverything you have written so far lives entirely in memory, so when the program ends, all of it disappears with it. A file is different. It sits on disk, and…https://exercises.lol/video-media/code_c_basics/text-files/text-files.enzh.mp4?v=17886164161502026-08-23yes https://exercises.lol/videos/code_c_basics/error-handling2026-09-05https://exercises.lol/video-media/code_c_basics/error-handling/error-handling.thumb.jpg?v=1788616517Error handlingIn many languages, a function that cannot do its job will throw an exception, and somewhere up the call chain someone catches it. C has nothing of the kind. A…https://exercises.lol/video-media/code_c_basics/error-handling/error-handling.enzh.mp4?v=17886165171392026-08-22yes https://exercises.lol/videos/code_c_basics/bits2026-09-05https://exercises.lol/video-media/code_c_basics/bits/bits.thumb.jpg?v=1788616512Bits and binaryInside the machine an int is not a decimal number; it is a row of bits, each one a nought or a one. Reading it works exactly like ordinary place value, except…https://exercises.lol/video-media/code_c_basics/bits/bits.enzh.mp4?v=17886165121502026-08-23yes https://exercises.lol/videos/code_c_basics/run-length-encoding2026-09-05https://exercises.lol/video-media/code_c_basics/run-length-encoding/run-length-encoding.thumb.jpg?v=1788616463Run-length encodingCompression makes data smaller, and run-length encoding is the simplest method there is. It looks for runs — stretches where the same character repeats. Take…https://exercises.lol/video-media/code_c_basics/run-length-encoding/run-length-encoding.enzh.mp4?v=17886164631392026-08-22yes https://exercises.lol/videos/code_c_basics/preprocessor2026-09-05https://exercises.lol/video-media/code_c_basics/preprocessor/preprocessor.thumb.jpg?v=1788616363Before the compilerSomething runs before the compiler ever sees your file. It is called the preprocessor, and it handles every line beginning with a hash. You have used it since…https://exercises.lol/video-media/code_c_basics/preprocessor/preprocessor.enzh.mp4?v=17886163631502026-08-23yes https://exercises.lol/videos/code_cyber_security/security-privacy2026-09-05https://exercises.lol/video-media/code_cyber_security/security-privacy/security-privacy.thumb.jpg?v=1788616672Security, privacy and integrityThree words get used as if they meant the same thing, and the exam asks you to separate them. Security is about keeping data and systems safe from people who…https://exercises.lol/video-media/code_cyber_security/security-privacy/security-privacy.enzh.mp4?v=17886166721282026-08-23yes https://exercises.lol/videos/code_cyber_security/malware2026-09-05https://exercises.lol/video-media/code_cyber_security/malware/malware.thumb.jpg?v=1788616674MalwareMalware is any program written to harm a computer or steal from it, and the exam names six kinds. Six names is a list to memorise unless you group them. Group…https://exercises.lol/video-media/code_cyber_security/malware/malware.enzh.mp4?v=17886166741292026-08-23yes https://exercises.lol/videos/code_cyber_security/attacks2026-09-05https://exercises.lol/video-media/code_cyber_security/attacks/attacks.thumb.jpg?v=1788616674Attacks and brute forceBeyond malware, attackers go at a system directly. A brute-force attack tries every possible password until one works — no cleverness, just patience and a fast…https://exercises.lol/video-media/code_cyber_security/attacks/attacks.enzh.mp4?v=17886166741252026-08-23yes https://exercises.lol/videos/code_cyber_security/social2026-09-05https://exercises.lol/video-media/code_cyber_security/social/social.thumb.jpg?v=1788616727Social engineeringEverything so far has attacked the machine. But the weakest part of a system is usually not the machine — it is a person, who can simply be asked. Social…https://exercises.lol/video-media/code_cyber_security/social/social.enzh.mp4?v=17886167271202026-08-23yes https://exercises.lol/videos/code_cyber_security/defences2026-09-05https://exercises.lol/video-media/code_cyber_security/defences/defences.thumb.jpg?v=1788616715Defending a systemDefences are usually given as a list, and that hides the point. Draw them as rings instead. An attacker coming from outside meets one wall after another: the…https://exercises.lol/video-media/code_cyber_security/defences/defences.enzh.mp4?v=17886167151232026-08-23yes https://exercises.lol/videos/code_cyber_security/authentication2026-09-05https://exercises.lol/video-media/code_cyber_security/authentication/authentication.thumb.jpg?v=1788616754Passwords and authenticationAuthentication means proving you are who you claim to be, and there are three classic ways. Something you know — a password or a PIN. Something you have — your…https://exercises.lol/video-media/code_cyber_security/authentication/authentication.enzh.mp4?v=17886167541162026-08-23yes https://exercises.lol/videos/code_cyber_security/hashing2026-09-05https://exercises.lol/video-media/code_cyber_security/hashing/hashing.thumb.jpg?v=1788616628Storing passwords safelyStart with what must never happen. If a site stores passwords as plain text and is breached, every password is readable the moment the file leaves the…https://exercises.lol/video-media/code_cyber_security/hashing/hashing.enzh.mp4?v=17886166281282026-08-23yes https://exercises.lol/videos/code_cyber_security/encoding2026-09-05https://exercises.lol/video-media/code_cyber_security/encoding/encoding.thumb.jpg?v=1788616665Encoding is not encryptionPeople say "encoded" when they mean "encrypted", and the two are not the same thing. Encoding changes the FORMAT of data so it can be stored or sent. It is not…https://exercises.lol/video-media/code_cyber_security/encoding/encoding.enzh.mp4?v=17886166651022026-08-23yes https://exercises.lol/videos/code_cyber_security/symmetric2026-09-05https://exercises.lol/video-media/code_cyber_security/symmetric/symmetric.thumb.jpg?v=1788616626Symmetric encryptionEncryption scrambles a message so that only someone with the key can read it. In symmetric encryption there is one key, and it does both jobs — watch, it…https://exercises.lol/video-media/code_cyber_security/symmetric/symmetric.enzh.mp4?v=17886166261192026-08-23yes https://exercises.lol/videos/code_cyber_security/asymmetric2026-09-05https://exercises.lol/video-media/code_cyber_security/asymmetric/asymmetric.thumb.jpg?v=1788616758Asymmetric encryptionLast lesson ended on a problem: you must share the secret key first. Asymmetric encryption answers it by using two keys instead of one. There is a public key…https://exercises.lol/video-media/code_cyber_security/asymmetric/asymmetric.enzh.mp4?v=17886167581272026-08-23yes https://exercises.lol/videos/code_cyber_security/signatures2026-09-05https://exercises.lol/video-media/code_cyber_security/signatures/signatures.thumb.jpg?v=1788616697Hashing and digital signaturesIn lesson seven we hashed passwords for secrecy. The same function does a second job: it protects integrity, which means proving that data was not changed.…https://exercises.lol/video-media/code_cyber_security/signatures/signatures.enzh.mp4?v=1788616697932026-08-23yes https://exercises.lol/videos/code_cyber_security/https2026-09-05https://exercises.lol/video-media/code_cyber_security/https/https.thumb.jpg?v=1788616674HTTPS, TLS and certificatesStart with something you look at every day. When the address begins with H T T P S and a padlock appears, your connection to that site is encrypted — nobody…https://exercises.lol/video-media/code_cyber_security/https/https.enzh.mp4?v=17886166741252026-08-23yes https://exercises.lol/videos/code_cyber_security/integrity2026-09-05https://exercises.lol/video-media/code_cyber_security/integrity/integrity.thumb.jpg?v=1788616652Data integrityIntegrity means data stays accurate, and two techniques protect it. They sound alike and the exam loves separating them, so watch what each one asks.…https://exercises.lol/video-media/code_cyber_security/integrity/integrity.enzh.mp4?v=1788616652882026-08-23yes https://exercises.lol/videos/code_cyber_security/sql-injection2026-09-05https://exercises.lol/video-media/code_cyber_security/sql-injection/sql-injection.thumb.jpg?v=1788616755SQL injectionMost apps look up a user by building a query out of a string. You type your name into a box, and the app glues what you typed into the query. Type Mei, and the…https://exercises.lol/video-media/code_cyber_security/sql-injection/sql-injection.enzh.mp4?v=17886167551212026-08-23yes https://exercises.lol/videos/code_cyber_security/least-privilege2026-09-05https://exercises.lol/video-media/code_cyber_security/least-privilege/least-privilege.thumb.jpg?v=1788616682Access control and least privilegeLeast privilege says: give every person and every program only the access they need, and no more. The reason is not tidiness — it is what happens after…https://exercises.lol/video-media/code_cyber_security/least-privilege/least-privilege.enzh.mp4?v=17886166821112026-08-23yes https://exercises.lol/videos/code_cyber_security/ethics2026-09-05https://exercises.lol/video-media/code_cyber_security/ethics/ethics.thumb.jpg?v=1788616759Ethics, law and staying safeYou have spent fifteen lessons learning how attacks work, and that knowledge comes with a duty. A computing professional uses these skills to protect people…https://exercises.lol/video-media/code_cyber_security/ethics/ethics.enzh.mp4?v=17886167591332026-08-23yes https://exercises.lol/videos/code_igcse_cs/sequence-io2026-09-05https://exercises.lol/video-media/code_igcse_cs/sequence-io/sequence-io.thumb.jpg?v=1788616873Sequence, input, outputThe syllabus starts with a word that sounds too simple to need naming: sequence. A program is a list of steps, and Python runs them from the top down, one at a…https://exercises.lol/video-media/code_igcse_cs/sequence-io/sequence-io.enzh.mp4?v=17886168731242026-08-23yes https://exercises.lol/videos/code_igcse_cs/variables-types2026-09-05https://exercises.lol/video-media/code_igcse_cs/variables-types/variables-types.thumb.jpg?v=1788616964Variables and typesA variable is a named box that holds a value. You put a value in with an equals sign, and that act has a name in the syllabus: assignment. Worth noticing…https://exercises.lol/video-media/code_igcse_cs/variables-types/variables-types.enzh.mp4?v=17886169641342026-08-23yes https://exercises.lol/videos/code_igcse_cs/selection2026-09-05https://exercises.lol/video-media/code_igcse_cs/selection/selection.thumb.jpg?v=1788616874SelectionSelection is the second big idea in the syllabus: choosing what to do, based on a test. The test gives back true or false, and the program goes one way if it…https://exercises.lol/video-media/code_igcse_cs/selection/selection.enzh.mp4?v=17886168741292026-08-23yes https://exercises.lol/videos/code_igcse_cs/iteration2026-09-05https://exercises.lol/video-media/code_igcse_cs/iteration/iteration.thumb.jpg?v=1788616868IterationIteration means repeating steps, and the everyday loop is the one that repeats a fixed number of times. In Python that is for i in range. Range on its own…https://exercises.lol/video-media/code_igcse_cs/iteration/iteration.enzh.mp4?v=17886168681372026-08-23yes https://exercises.lol/videos/code_igcse_cs/totalling2026-09-05https://exercises.lol/video-media/code_igcse_cs/totalling/totalling.thumb.jpg?v=1788616872Totalling and countingAdding up a list of numbers has a name in the syllabus: totalling. It works with one extra variable that remembers the answer so far. The total starts at…https://exercises.lol/video-media/code_igcse_cs/totalling/totalling.enzh.mp4?v=17886168721272026-08-23yes https://exercises.lol/videos/code_igcse_cs/procedures2026-09-05https://exercises.lol/video-media/code_igcse_cs/procedures/procedures.thumb.jpg?v=1788616903Procedures and functionsA function is a named block of code. You write it once with def, and then run it whenever you like by writing its name. Here it is called twice, so it prints…https://exercises.lol/video-media/code_igcse_cs/procedures/procedures.enzh.mp4?v=17886169031342026-08-23yes https://exercises.lol/videos/code_igcse_cs/validation2026-09-05https://exercises.lol/video-media/code_igcse_cs/validation/validation.thumb.jpg?v=1788616884ValidationWhatever you ask for, someone will type something else. An age of forty-five is fine. An age of nine hundred is not, and neither is a negative age — but the…https://exercises.lol/video-media/code_igcse_cs/validation/validation.enzh.mp4?v=17886168841422026-08-23yes https://exercises.lol/videos/code_igcse_cs/arrays2026-09-05https://exercises.lol/video-media/code_igcse_cs/arrays/arrays.thumb.jpg?v=1788616826ArraysSuppose you have three scores. You could use three variables — but then thirty scores needs thirty names, and you cannot write a loop over names. An array…https://exercises.lol/video-media/code_igcse_cs/arrays/arrays.enzh.mp4?v=17886168261322026-08-23yes https://exercises.lol/videos/code_igcse_cs/two-d-arrays2026-09-05https://exercises.lol/video-media/code_igcse_cs/two-d-arrays/two-d-arrays.thumb.jpg?v=1788616959Two-dimensional arraysA table of marks, a seating plan, a game board — these have rows and columns, and one index is not enough. A two-dimensional array is a list of lists: each…https://exercises.lol/video-media/code_igcse_cs/two-d-arrays/two-d-arrays.enzh.mp4?v=17886169591232026-08-23yes https://exercises.lol/videos/code_igcse_cs/searching2026-09-05https://exercises.lol/video-media/code_igcse_cs/searching/searching.thumb.jpg?v=1788616965Searching, max and minA linear search looks at each item in turn until it finds what it wants, and stops as soon as it finds it. The syllabus names it, so expect the phrase on the…https://exercises.lol/video-media/code_igcse_cs/searching/searching.enzh.mp4?v=17886169651272026-08-23yes https://exercises.lol/videos/code_igcse_cs/bubble-sort2026-09-05https://exercises.lol/video-media/code_igcse_cs/bubble-sort/bubble-sort.thumb.jpg?v=1788616860Bubble sortEvery sort is built on one move: exchanging two values. Python has a shortcut that does it in a single line. The exam does not, and wants three lines and a…https://exercises.lol/video-media/code_igcse_cs/bubble-sort/bubble-sort.enzh.mp4?v=17886168601222026-08-23yes https://exercises.lol/videos/code_igcse_cs/files2026-09-05https://exercises.lol/video-media/code_igcse_cs/files/files.thumb.jpg?v=1788616964Text filesVariables vanish when a program ends; a file does not. Working with one always takes three steps, and the exam expects all three. Open the file, naming it and…https://exercises.lol/video-media/code_igcse_cs/files/files.enzh.mp4?v=17886169641282026-08-23yes https://exercises.lol/videos/code_igcse_cs/sql2026-09-05https://exercises.lol/video-media/code_igcse_cs/sql/sql.thumb.jpg?v=1788616821Databases and SQLA database keeps data in tables, and a table looks like a spreadsheet: rows and columns. Each row holds everything about one thing — one student here — and it…https://exercises.lol/video-media/code_igcse_cs/sql/sql.enzh.mp4?v=17886168211292026-08-23yes https://exercises.lol/videos/code_igcse_cs/logic2026-09-05https://exercises.lol/video-media/code_igcse_cs/logic/logic.thumb.jpg?v=1788616905Boolean logicA Boolean value is either true or false, and there are exactly three operators that combine them. AND is true only when both sides are true. OR is true when at…https://exercises.lol/video-media/code_igcse_cs/logic/logic.enzh.mp4?v=17886169051392026-08-23yes https://exercises.lol/videos/code_javascript/console-log2026-09-05https://exercises.lol/video-media/code_javascript/console-log/console-log.thumb.jpg?v=1788617177console.log and commentsJavaScript is the language your browser already speaks. It runs inside the page you are looking at — no installing, no setting up, it is simply there. And the…https://exercises.lol/video-media/code_javascript/console-log/console-log.enzh.mp4?v=17886171771572026-08-23yes https://exercises.lol/videos/code_javascript/variables2026-09-05https://exercises.lol/video-media/code_javascript/variables/variables.thumb.jpg?v=1788617164Variables — let and constA variable is a box with a name on it. This line makes a box called city and puts the word Cairo into the box. Notice the word at the front — const — which is…https://exercises.lol/video-media/code_javascript/variables/variables.enzh.mp4?v=17886171641392026-08-23yes https://exercises.lol/videos/code_javascript/numbers2026-09-05https://exercises.lol/video-media/code_javascript/numbers/numbers.thumb.jpg?v=1788617082Numbers and mathsJavaScript does arithmetic without being taught. Plus and minus and star add, subtract, multiply — and the answers come straight back in the console. Then look…https://exercises.lol/video-media/code_javascript/numbers/numbers.enzh.mp4?v=17886170821272026-08-23yes https://exercises.lol/videos/code_javascript/strings2026-09-05https://exercises.lol/video-media/code_javascript/strings/strings.thumb.jpg?v=1788617085StringsA string is text in quotes, and a plus between two strings joins them — concatenation, if you want the proper word. Here the greeting is built from three…https://exercises.lol/video-media/code_javascript/strings/strings.enzh.mp4?v=17886170851522026-08-23yes https://exercises.lol/videos/code_javascript/template-literals2026-09-05https://exercises.lol/video-media/code_javascript/template-literals/template-literals.thumb.jpg?v=1788617031Template literalsYou already know how to build a sentence out of pieces: joining with pluses. It works, and it gets ugly fast — four fragments, two pluses, quotes opening and…https://exercises.lol/video-media/code_javascript/template-literals/template-literals.enzh.mp4?v=17886170311422026-08-23yes https://exercises.lol/videos/code_javascript/booleans2026-09-05https://exercises.lol/video-media/code_javascript/booleans/booleans.thumb.jpg?v=1788617136Booleans and comparisonsSo far your values have been numbers and strings. Here is a third kind, and it has only two values in the whole world: true and false. It is called a boolean…https://exercises.lol/video-media/code_javascript/booleans/booleans.enzh.mp4?v=17886171361482026-08-23yes https://exercises.lol/videos/code_javascript/if-else2026-09-05https://exercises.lol/video-media/code_javascript/if-else/if-else.thumb.jpg?v=1788617104if / elseAn if in JavaScript has a shape you copy exactly. The word if, then round brackets holding the test — the boolean you learned to write last lesson. Then curly…https://exercises.lol/video-media/code_javascript/if-else/if-else.enzh.mp4?v=17886171041402026-08-23yes https://exercises.lol/videos/code_javascript/for-loops2026-09-05https://exercises.lol/video-media/code_javascript/for-loops/for-loops.thumb.jpg?v=1788617039for loopsA JavaScript for loop packs three separate jobs into one set of brackets, separated by two semicolons. The first part sets the counter up, and it runs once…https://exercises.lol/video-media/code_javascript/for-loops/for-loops.enzh.mp4?v=17886170391532026-08-23yes https://exercises.lol/videos/code_javascript/while-loops2026-09-05https://exercises.lol/video-media/code_javascript/while-loops/while-loops.thumb.jpg?v=1788617174while loopsA for loop is right when the number of passes is written down in the loop itself — one to five is five passes, and you can see it. But now suppose you start at…https://exercises.lol/video-media/code_javascript/while-loops/while-loops.enzh.mp4?v=17886171741452026-08-23yes https://exercises.lol/videos/code_javascript/functions2026-09-05https://exercises.lol/video-media/code_javascript/functions/functions.thumb.jpg?v=1788617064FunctionsA function is a job with a name. You write the word function, which tells JavaScript you are defining something rather than running it — nothing in the body…https://exercises.lol/video-media/code_javascript/functions/functions.enzh.mp4?v=17886170641382026-08-23yes https://exercises.lol/videos/code_javascript/arrow-functions2026-09-05https://exercises.lol/video-media/code_javascript/arrow-functions/arrow-functions.thumb.jpg?v=1788617076Arrow functionsStart with the function you already know how to write. First, give the function a name by storing it in a const, instead of naming it after the word function.…https://exercises.lol/video-media/code_javascript/arrow-functions/arrow-functions.enzh.mp4?v=17886170761162026-08-23yes https://exercises.lol/videos/code_javascript/arrays2026-09-05https://exercises.lol/video-media/code_javascript/arrays/arrays.thumb.jpg?v=1788617085ArraysAn array holds several values in order, under one name, written in square brackets. Each item sits at a numbered position, counting from zero — the same…https://exercises.lol/video-media/code_javascript/arrays/arrays.enzh.mp4?v=17886170851412026-08-23yes https://exercises.lol/videos/code_javascript/array-methods2026-09-05https://exercises.lol/video-media/code_javascript/array-methods/array-methods.thumb.jpg?v=1788617082Array methodsDoubling every number in an array is something you can already do: make an empty array, write the loop yourself, push each doubled value. Four lines, an index…https://exercises.lol/video-media/code_javascript/array-methods/array-methods.enzh.mp4?v=17886170821332026-08-23yes https://exercises.lol/videos/code_javascript/objects2026-09-05https://exercises.lol/video-media/code_javascript/objects/objects.thumb.jpg?v=1788617122ObjectsAn array holds a list of similar things. An object holds different facts about ONE thing. You could keep a book's title and page count in two separate…https://exercises.lol/video-media/code_javascript/objects/objects.enzh.mp4?v=17886171221372026-08-23yes https://exercises.lol/videos/code_javascript/putting-it-together2026-09-05https://exercises.lol/video-media/code_javascript/putting-it-together/putting-it-together.thumb.jpg?v=1788617178Putting it togetherOne more loop before the end, and it is the one you will reach for most. The version you know needs a counter and an index — three things to write, and an…https://exercises.lol/video-media/code_javascript/putting-it-together/putting-it-together.enzh.mp4?v=17886171781242026-08-23yes https://exercises.lol/videos/code_latex/first-document2026-09-05https://exercises.lol/video-media/code_latex/first-document/first-document.thumb.jpg?v=1788617289Your first documentLaTeX is how most maths and science documents are made. You do not drag boxes around; you write plain text with commands in it, and a program turns that into a…https://exercises.lol/video-media/code_latex/first-document/first-document.enzh.mp4?v=17886172891212026-08-23yes https://exercises.lol/videos/code_latex/sections2026-09-05https://exercises.lol/video-media/code_latex/sections/sections.thumb.jpg?v=1788630839Sections and titlesReal documents are split into sections so a reader can follow them, and the command is simply section with the title in braces. Look at what came out: a…https://exercises.lol/video-media/code_latex/sections/sections.enzh.mp4?v=17886308391202026-08-23yes https://exercises.lol/videos/code_latex/emphasis2026-09-05https://exercises.lol/video-media/code_latex/emphasis/emphasis.thumb.jpg?v=1788617299Bold, italic and emphasisTo change how a word looks, you wrap it in a command — the same backslash, name and braces from lesson one. Textbf sets it bold. Textit sets it italic. Texttt…https://exercises.lol/video-media/code_latex/emphasis/emphasis.enzh.mp4?v=17886172991392026-08-23yes https://exercises.lol/videos/code_latex/lists2026-09-05https://exercises.lol/video-media/code_latex/lists/lists.thumb.jpg?v=1788617324Bulleted and numbered listsA list is your first ENVIRONMENT, which is the second shape in LaTeX after the command. It opens with begin and a name, holds your content, and closes with end…https://exercises.lol/video-media/code_latex/lists/lists.enzh.mp4?v=17886173241172026-08-23yes https://exercises.lol/videos/code_latex/maths2026-09-05https://exercises.lol/video-media/code_latex/maths/maths.thumb.jpg?v=1788617244Maths — your first formulaThis is what LaTeX is famous for. Put dollar signs around something and everything between them is set as MATHS. Look at what changes: the letters lean, the…https://exercises.lol/video-media/code_latex/maths/maths.enzh.mp4?v=17886172441182026-08-23yes https://exercises.lol/videos/code_latex/amsmath2026-09-05https://exercises.lol/video-media/code_latex/amsmath/amsmath.thumb.jpg?v=1788617244Fractions, roots and sumsBefore the maths, one new idea: a package. A package adds commands LaTeX does not have on its own, and you load it in the preamble with usepackage. Amsmath is…https://exercises.lol/video-media/code_latex/amsmath/amsmath.enzh.mp4?v=17886172441182026-08-23yes https://exercises.lol/videos/code_latex/align2026-09-05https://exercises.lol/video-media/code_latex/align/align.thumb.jpg?v=1788617378Aligning equationsWhen you show working, a reader follows it by the equals signs. Set each line as its own equation and they scatter. Line them up instead and the eye runs…https://exercises.lol/video-media/code_latex/align/align.enzh.mp4?v=17886173781142026-08-23yes https://exercises.lol/videos/code_latex/tables2026-09-05https://exercises.lol/video-media/code_latex/tables/tables.thumb.jpg?v=1788617321TablesA table is the tabular environment, and it takes something no other environment has taken so far: a column specification, in braces after the name. Those…https://exercises.lol/video-media/code_latex/tables/tables.enzh.mp4?v=17886173211202026-08-23yes https://exercises.lol/videos/code_latex/tikz2026-09-05https://exercises.lol/video-media/code_latex/tikz/tikz.thumb.jpg?v=1788617371Drawing with TikZYou can draw diagrams with code, without any image file, using the TikZ package. Load it once, then draw inside a tikzpicture environment. Draw from nought…https://exercises.lol/video-media/code_latex/tikz/tikz.enzh.mp4?v=17886173711242026-08-23yes https://exercises.lol/videos/code_latex/refs2026-09-05https://exercises.lol/video-media/code_latex/refs/refs.thumb.jpg?v=1788617370Labels and cross-referencesLesson two showed headings renumbering themselves, and left a gap. Here it is. The sentence says "as shown in Section 2". Add a section above Methods and…https://exercises.lol/video-media/code_latex/refs/refs.enzh.mp4?v=17886173701242026-08-23yes https://exercises.lol/videos/code_latex/citations2026-09-05https://exercises.lol/video-media/code_latex/citations/citations.thumb.jpg?v=1788617289Citations and bibliographyAcademic writing has to say where facts came from, and LaTeX handles it with the idea you learned last lesson. Look at the two pairs: label and ref for a…https://exercises.lol/video-media/code_latex/citations/citations.enzh.mp4?v=17886172891172026-08-23yes https://exercises.lol/videos/code_latex/geometry2026-09-05https://exercises.lol/video-media/code_latex/geometry/geometry.thumb.jpg?v=1788630917Page layout and marginsBefore the command, the shape. The outer rectangle is the paper. The lines inside it are the text block — where words are allowed to go. And the gap between…https://exercises.lol/video-media/code_latex/geometry/geometry.enzh.mp4?v=17886309171162026-08-23yes https://exercises.lol/videos/code_latex/colour2026-09-05https://exercises.lol/video-media/code_latex/colour/colour.thumb.jpg?v=1788630840Colour and linksColour comes from the xcolor package. Load it in the preamble, then wrap words in textcolor with the colour name first and the words second. Notice the shape…https://exercises.lol/video-media/code_latex/colour/colour.enzh.mp4?v=17886308401212026-08-23yes https://exercises.lol/videos/code_latex/report2026-09-05https://exercises.lol/video-media/code_latex/report/report.thumb.jpg?v=1788617286Capstone: a one-page reportLook at what thirteen lessons have given you. Section, for structure that numbers itself. Textbf and emph, for the way words look. Dollars and frac, for the…https://exercises.lol/video-media/code_latex/report/report.enzh.mp4?v=17886172861222026-08-23yes https://exercises.lol/videos/code_linux/prompt2026-09-05https://exercises.lol/video-media/code_linux/prompt/prompt.thumb.jpg?v=1788617557The shell and the promptWhen the terminal is ready it shows a prompt and waits. Most people look straight past it, and it is already telling you three things. The first word is who…https://exercises.lol/video-media/code_linux/prompt/prompt.enzh.mp4?v=17886175571202026-08-23yes https://exercises.lol/videos/code_linux/moving2026-09-05https://exercises.lol/video-media/code_linux/moving/moving.thumb.jpg?v=1788617559Moving aroundFolders — Linux calls them directories — hold files and other folders, and the whole lot is one tree. A single slash at the top is the root, and there is…https://exercises.lol/video-media/code_linux/moving/moving.enzh.mp4?v=17886175591282026-08-23yes https://exercises.lol/videos/code_linux/reading2026-09-05https://exercises.lol/video-media/code_linux/reading/reading.thumb.jpg?v=1788617539Reading filesThe simplest way to read a file is c a t, which prints the whole thing straight to the screen. Four lines in the file, four lines of output. The odd name is…https://exercises.lol/video-media/code_linux/reading/reading.enzh.mp4?v=17886175391152026-08-23yes https://exercises.lol/videos/code_linux/creating2026-09-05https://exercises.lol/video-media/code_linux/creating/creating.thumb.jpg?v=1788617558Creating and removingTwo commands make things. M k d i r makes a directory — a folder. Touch makes a file. And note what kind of file: touch makes it empty, zero bytes, but it…https://exercises.lol/video-media/code_linux/creating/creating.enzh.mp4?v=17886175581512026-08-23yes https://exercises.lol/videos/code_linux/wildcards2026-09-05https://exercises.lol/video-media/code_linux/wildcards/wildcards.thumb.jpg?v=1788617473WildcardsA wildcard is a symbol that stands for "anything", and it turns one command into a command about many files. Star dot t x t means every name ending in .txt…https://exercises.lol/video-media/code_linux/wildcards/wildcards.enzh.mp4?v=17886174731242026-08-23yes https://exercises.lol/videos/code_linux/redirection2026-09-05https://exercises.lol/video-media/code_linux/redirection/redirection.thumb.jpg?v=1788617490Saving output to filesNormally a command's output appears on screen. Add an arrow and a filename and it does not — and the first time, that looks like nothing happened. It did: the…https://exercises.lol/video-media/code_linux/redirection/redirection.enzh.mp4?v=17886174901142026-08-23yes https://exercises.lol/videos/code_linux/pipes2026-09-05https://exercises.lol/video-media/code_linux/pipes/pipes.thumb.jpg?v=1788617513Pipes — joining commandsThis is the idea the command line is built on. A pipe sends one command's output straight into sort, as its input. Cat produces five lines; sort receives those…https://exercises.lol/video-media/code_linux/pipes/pipes.enzh.mp4?v=17886175131212026-08-23yes https://exercises.lol/videos/code_linux/grep2026-09-05https://exercises.lol/video-media/code_linux/grep/grep.thumb.jpg?v=1788617487Searching with grepGrep searches for a word and prints only the lines that contain it. Give it error and this log file, and out of five lines, one comes back. On a file this…https://exercises.lol/video-media/code_linux/grep/grep.enzh.mp4?v=17886174871182026-08-23yes https://exercises.lol/videos/code_linux/find2026-09-05https://exercises.lol/video-media/code_linux/find/find.thumb.jpg?v=1788617487Finding files with findYou have known l s since lesson two, and it has one limit: it shows only what is right here, in this one folder. Find does not stop there. It walks every…https://exercises.lol/video-media/code_linux/find/find.enzh.mp4?v=17886174871192026-08-23yes https://exercises.lol/videos/code_linux/sorting2026-09-05https://exercises.lol/video-media/code_linux/sorting/sorting.thumb.jpg?v=1788617563Sorting and columnsSort arranges lines in alphabetical order. Three fruits go in unordered and come back apple, fig, pear. Dash r turns it round and gives you the reverse. Sort…https://exercises.lol/video-media/code_linux/sorting/sorting.enzh.mp4?v=17886175631402026-08-23yes https://exercises.lol/videos/code_linux/permissions2026-09-05https://exercises.lol/video-media/code_linux/permissions/permissions.thumb.jpg?v=1788617449File permissionsRun l s dash l and every line starts with ten characters that look like line noise. They are not. They are four fields: one, then three threes. The first…https://exercises.lol/video-media/code_linux/permissions/permissions.enzh.mp4?v=17886174491402026-08-23yes https://exercises.lol/videos/code_linux/users2026-09-05https://exercises.lol/video-media/code_linux/users/users.thumb.jpg?v=1788617488Users and sudoLinux was built from the start for many people to share one machine safely. Each person gets an account, and your files are yours: you cannot read or change…https://exercises.lol/video-media/code_linux/users/users.enzh.mp4?v=17886174881192026-08-23yes https://exercises.lol/videos/code_linux/processes2026-09-05https://exercises.lol/video-media/code_linux/processes/processes.thumb.jpg?v=1788617438Programs and processesTwo words that sound the same and are not. A program is a file sitting on disk, doing nothing. A process is that file running — your browser, your editor, and…https://exercises.lol/video-media/code_linux/processes/processes.enzh.mp4?v=17886174381232026-08-23yes https://exercises.lol/videos/code_linux/next-steps2026-09-05https://exercises.lol/video-media/code_linux/next-steps/next-steps.thumb.jpg?v=1788617517Software, settings, next stepsOn Linux you almost never download an installer. A package manager fetches software for you, from a checked source. The same idea has different names on…https://exercises.lol/video-media/code_linux/next-steps/next-steps.enzh.mp4?v=17886175171472026-08-23yes https://exercises.lol/videos/code_pseudocode/sequence-output2026-09-05https://exercises.lol/video-media/code_pseudocode/sequence-output/sequence-output.thumb.jpg?v=1788617643OUTPUT and sequenceCambridge exams write algorithms in pseudocode — not Python, not Java. It is a real notation with real keywords, and the paper expects those exact words. Here…https://exercises.lol/video-media/code_pseudocode/sequence-output/sequence-output.enzh.mp4?v=17886176431182026-08-23yes https://exercises.lol/videos/code_pseudocode/variables2026-09-05https://exercises.lol/video-media/code_pseudocode/variables/variables.thumb.jpg?v=1788617682Variables and DECLAREA variable is a named store that holds one value. The arrow is how a value gets in — read it as "store sixteen into Age", and watch it happen: the sixteen goes…https://exercises.lol/video-media/code_pseudocode/variables/variables.enzh.mp4?v=17886176821072026-08-23yes https://exercises.lol/videos/code_pseudocode/input-types2026-09-05https://exercises.lol/video-media/code_pseudocode/input-types/input-types.thumb.jpg?v=1788617688INPUT and data typesINPUT reads one line that the user types and stores it in the variable you name. That is the whole statement — no prompt, no brackets. Pair it with an OUTPUT…https://exercises.lol/video-media/code_pseudocode/input-types/input-types.enzh.mp4?v=17886176881022026-08-23yes https://exercises.lol/videos/code_pseudocode/arithmetic2026-09-05https://exercises.lol/video-media/code_pseudocode/arithmetic/arithmetic.thumb.jpg?v=1788617645Arithmetic, DIV and MODPlus, minus, times and slash behave exactly as you would expect, and there is nothing to memorise about the first three. The fourth is worth a second look.…https://exercises.lol/video-media/code_pseudocode/arithmetic/arithmetic.enzh.mp4?v=17886176451242026-08-23yes https://exercises.lol/videos/code_pseudocode/selection-if2026-09-05https://exercises.lol/video-media/code_pseudocode/selection-if/selection-if.thumb.jpg?v=1788617678Selection: IFSelection is the second control structure, and it is one test with exactly two exits. If the test is true, the program takes the TRUE exit and runs the block…https://exercises.lol/video-media/code_pseudocode/selection-if/selection-if.enzh.mp4?v=17886176781242026-08-23yes https://exercises.lol/videos/code_pseudocode/selection-case2026-09-05https://exercises.lol/video-media/code_pseudocode/selection-case/selection-case.thumb.jpg?v=1788617727Selection: CASEWhen one variable is checked against several fixed values, a stack of IFs gets long. CASE says the same thing in one block. Grade holds two. CASE compares it…https://exercises.lol/video-media/code_pseudocode/selection-case/selection-case.enzh.mp4?v=17886177271192026-08-23yes https://exercises.lol/videos/code_pseudocode/iteration-for2026-09-05https://exercises.lol/video-media/code_pseudocode/iteration-for/iteration-for.thumb.jpg?v=1788617679Iteration: FORIteration is the third control structure, and a FOR loop is the version you use when you already know how many times. It has exactly one moving part: the…https://exercises.lol/video-media/code_pseudocode/iteration-for/iteration-for.enzh.mp4?v=17886176791272026-08-23yes https://exercises.lol/videos/code_pseudocode/iteration-while2026-09-05https://exercises.lol/video-media/code_pseudocode/iteration-while/iteration-while.thumb.jpg?v=1788617748Iteration: WHILE and REPEATWhen you do not know how many repeats you need, the test moves into the loop itself. In a WHILE loop the test is at the top: it is checked before you are let…https://exercises.lol/video-media/code_pseudocode/iteration-while/iteration-while.enzh.mp4?v=17886177481302026-08-23yes https://exercises.lol/videos/code_pseudocode/strings2026-09-05https://exercises.lol/video-media/code_pseudocode/strings/strings.thumb.jpg?v=1788617765String handlingThree of the string functions have nothing to trip on. LENGTH gives how many characters are in a string — hello is five. UCASE returns it in capitals, and…https://exercises.lol/video-media/code_pseudocode/strings/strings.enzh.mp4?v=17886177651262026-08-23yes https://exercises.lol/videos/code_pseudocode/arrays-1d2026-09-05https://exercises.lol/video-media/code_pseudocode/arrays-1d/arrays-1d.thumb.jpg?v=17886177591-D arraysAn array stores many values under one name, and the declaration says exactly three things. Score is one name for all of them. The two numbers in brackets are…https://exercises.lol/video-media/code_pseudocode/arrays-1d/arrays-1d.enzh.mp4?v=17886177591182026-08-23yes https://exercises.lol/videos/code_pseudocode/arrays-2d2026-09-05https://exercises.lol/video-media/code_pseudocode/arrays-2d/arrays-2d.thumb.jpg?v=17886176802-D arraysA 2-D array is a grid — a table with rows and columns. The declaration has two index pairs instead of one, and each pair does the same job it did in lesson…https://exercises.lol/video-media/code_pseudocode/arrays-2d/arrays-2d.enzh.mp4?v=17886176801282026-08-23yes https://exercises.lol/videos/code_pseudocode/procedures2026-09-05https://exercises.lol/video-media/code_pseudocode/procedures/procedures.thumb.jpg?v=1788617767ProceduresA procedure is a named block of steps. You write it once, between PROCEDURE and ENDPROCEDURE, and then run it with CALL — as many times as you like. And notice…https://exercises.lol/video-media/code_pseudocode/procedures/procedures.enzh.mp4?v=17886177671212026-08-23yes https://exercises.lol/videos/code_pseudocode/functions2026-09-05https://exercises.lol/video-media/code_pseudocode/functions/functions.thumb.jpg?v=1788617678FunctionsA function works something out and hands the answer back. Two words do that, and they are easy to mix up because they differ by one letter. RETURNS, with an S…https://exercises.lol/video-media/code_pseudocode/functions/functions.enzh.mp4?v=17886176781212026-08-23yes https://exercises.lol/videos/code_pseudocode/standard-methods2026-09-05https://exercises.lol/video-media/code_pseudocode/standard-methods/standard-methods.thumb.jpg?v=1788617766Putting it togetherCambridge names four standard methods — totalling, counting, linear search, and finding the maximum or minimum — and it is tempting to learn them as four…https://exercises.lol/video-media/code_pseudocode/standard-methods/standard-methods.enzh.mp4?v=17886177661222026-08-23yes https://exercises.lol/videos/code_python_basics/first-program2026-09-05https://exercises.lol/video-media/code_python_basics/first-program/first-program.thumb.jpg?v=1788615483Your first programA computer is not clever. It cannot guess what you meant. It does exactly what you tell it, and nothing else. You write a line of instructions. Python reads…https://exercises.lol/video-media/code_python_basics/first-program/first-program.enzh.mp4?v=17886154832252026-08-22yes https://exercises.lol/videos/code_python_basics/variables2026-09-05https://exercises.lol/video-media/code_python_basics/variables/variables.thumb.jpg?v=1788615568VariablesSuppose your program mentions the same city three times. You could type it again, and again, and again — and then the day comes when the city changes, and you…https://exercises.lol/video-media/code_python_basics/variables/variables.enzh.mp4?v=17886155682172026-08-22yes https://exercises.lol/videos/code_python_basics/numbers-operators2026-09-05https://exercises.lol/video-media/code_python_basics/numbers-operators/numbers-operators.thumb.jpg?v=1788615613Numbers & operatorsYou do not have to teach Python arithmetic — it already knows. Write plus, minus, times, and it answers nine, five and fourteen without being told what those…https://exercises.lol/video-media/code_python_basics/numbers-operators/numbers-operators.enzh.mp4?v=17886156131872026-08-23yes https://exercises.lol/videos/code_python_basics/getting-input2026-09-05https://exercises.lol/video-media/code_python_basics/getting-input/getting-input.thumb.jpg?v=1788615407Getting inputEvery program so far has known everything in advance. Here the greeting works perfectly — for Sam. You wrote the name into the program, so Sam is the only…https://exercises.lol/video-media/code_python_basics/getting-input/getting-input.enzh.mp4?v=17886154071762026-08-22yes https://exercises.lol/videos/code_python_basics/strings2026-09-05https://exercises.lol/video-media/code_python_basics/strings/strings.thumb.jpg?v=1788615500Working with stringsA string is a row of characters, and each one sits in a numbered position called an index. Here is the surprise that trips up every beginner: counting starts…https://exercises.lol/video-media/code_python_basics/strings/strings.enzh.mp4?v=17886155001802026-08-22yes https://exercises.lol/videos/code_python_basics/making-decisions2026-09-05https://exercises.lol/video-media/code_python_basics/making-decisions/making-decisions.thumb.jpg?v=1788615419Making decisionsEverything you have written so far does the same thing every time it runs. Real programs need to choose. So you ask a question with a true-or-false answer — is…https://exercises.lol/video-media/code_python_basics/making-decisions/making-decisions.enzh.mp4?v=17886154192112026-08-23yes https://exercises.lol/videos/code_python_basics/counting-loops2026-09-05https://exercises.lol/video-media/code_python_basics/counting-loops/counting-loops.thumb.jpg?v=1788615613Counting loopsTo print the numbers one to five you could write it five times. It works. Now print one to five hundred, and the idea collapses — nobody types five hundred…https://exercises.lol/video-media/code_python_basics/counting-loops/counting-loops.enzh.mp4?v=17886156131822026-08-22yes https://exercises.lol/videos/code_python_basics/while-loops2026-09-05https://exercises.lol/video-media/code_python_basics/while-loops/while-loops.thumb.jpg?v=1788615584While loopsA for loop is perfect when you know the count in advance: print one to five, five passes, done. But now think about asking someone a question until they type…https://exercises.lol/video-media/code_python_basics/while-loops/while-loops.enzh.mp4?v=17886155841802026-08-23yes https://exercises.lol/videos/code_python_basics/lists2026-09-05https://exercises.lol/video-media/code_python_basics/lists/lists.thumb.jpg?v=1788615330ListsFive test scores, and so far you would give them a name each: score one, score two, and so on. It works until you need to add them up, and then you are writing…https://exercises.lol/video-media/code_python_basics/lists/lists.enzh.mp4?v=17886153301672026-08-22yes https://exercises.lol/videos/code_python_basics/functions2026-09-05https://exercises.lol/video-media/code_python_basics/functions/functions.thumb.jpg?v=1788615556FunctionsYou have written the same four lines twice: total starts at zero, loop, divide by the length. If a third list turns up you will copy it again — and the day you…https://exercises.lol/video-media/code_python_basics/functions/functions.enzh.mp4?v=17886155561722026-08-22yes https://exercises.lol/videos/code_python_basics/scope-arguments2026-09-05https://exercises.lol/video-media/code_python_basics/scope-arguments/scope-arguments.thumb.jpg?v=1788615345Scope & argumentsThink of your program as a room, and every function call as a smaller room inside it. A variable made inside the function belongs to that small room: it is…https://exercises.lol/video-media/code_python_basics/scope-arguments/scope-arguments.enzh.mp4?v=17886153451842026-08-23yes https://exercises.lol/videos/code_python_basics/dictionaries2026-09-05https://exercises.lol/video-media/code_python_basics/dictionaries/dictionaries.thumb.jpg?v=1788615535DictionariesStore a book in a list and you have to remember which position holds what. Was slot one the number of pages, or the year? Six months later you will guess…https://exercises.lol/video-media/code_python_basics/dictionaries/dictionaries.enzh.mp4?v=17886155351552026-08-22yes https://exercises.lol/videos/code_python_basics/planning2026-09-05https://exercises.lol/video-media/code_python_basics/planning/planning.thumb.jpg?v=1788615423Planning & pseudocodeWhen a task gets hard, the temptation is to start typing and hope. The faster way is to write the steps down in ordinary sentences first. Read the number.…https://exercises.lol/video-media/code_python_basics/planning/planning.enzh.mp4?v=17886154232022026-08-23yes https://exercises.lol/videos/code_python_basics/errors-testing2026-09-05https://exercises.lol/video-media/code_python_basics/errors-testing/errors-testing.thumb.jpg?v=1788615528Errors & testingErrors come in three kinds, and telling them apart tells you where to look. A syntax error breaks Python's own rules — a missing bracket, a missing colon — so…https://exercises.lol/video-media/code_python_basics/errors-testing/errors-testing.enzh.mp4?v=17886155281802026-08-22yes https://exercises.lol/videos/code_python_basics/putting-it-together2026-09-05https://exercises.lol/video-media/code_python_basics/putting-it-together/putting-it-together.thumb.jpg?v=1788615398Putting it all togetherThis is the last lesson, and it builds one small tool out of everything so far. You start with one list of scores. You want to know the average, how many…https://exercises.lol/video-media/code_python_basics/putting-it-together/putting-it-together.enzh.mp4?v=17886153981472026-08-22yes https://exercises.lol/videos/code_sql_databases/databases-select2026-09-05https://exercises.lol/video-media/code_sql_databases/databases-select/databases-select.thumb.jpg?v=1788617930Databases and SELECTA database stores information in tables, and a table is a grid — not unlike a spreadsheet. Across, one row is one record: everything known about one student.…https://exercises.lol/video-media/code_sql_databases/databases-select/databases-select.enzh.mp4?v=17886179301272026-08-23yes https://exercises.lol/videos/code_sql_databases/choosing-columns2026-09-05https://exercises.lol/video-media/code_sql_databases/choosing-columns/choosing-columns.thumb.jpg?v=1788617866Choosing columnsA star gives you every column, and usually you want only a few. So instead of the star, list the ones you want, separated by commas. The result keeps the two…https://exercises.lol/video-media/code_sql_databases/choosing-columns/choosing-columns.enzh.mp4?v=1788617866852026-08-23yes https://exercises.lol/videos/code_sql_databases/where2026-09-05https://exercises.lol/video-media/code_sql_databases/where/where.thumb.jpg?v=1788617910Filtering with WHEREEvery query so far returned all the rows. WHERE changes that: it keeps only the rows that match a condition. Scores of eighty or more, and the other two…https://exercises.lol/video-media/code_sql_databases/where/where.enzh.mp4?v=17886179101172026-08-23yes https://exercises.lol/videos/code_sql_databases/and-or-not2026-09-05https://exercises.lol/video-media/code_sql_databases/and-or-not/and-or-not.thumb.jpg?v=1788617971AND, OR and NOTA WHERE can test more than one thing. AND requires both to be true. Take form equals eleven A on its own and three survive: Mei, Sara and Lin. Now add AND…https://exercises.lol/video-media/code_sql_databases/and-or-not/and-or-not.enzh.mp4?v=17886179711252026-08-23yes https://exercises.lol/videos/code_sql_databases/order-by2026-09-05https://exercises.lol/video-media/code_sql_databases/order-by/order-by.thumb.jpg?v=1788618012Sorting with ORDER BYRows come back in no particular order. It usually LOOKS like insertion order, but nothing promises that, and a database is free to change it. ORDER BY is how…https://exercises.lol/video-media/code_sql_databases/order-by/order-by.enzh.mp4?v=17886180121192026-08-23yes https://exercises.lol/videos/code_sql_databases/aggregates2026-09-05https://exercises.lol/video-media/code_sql_databases/aggregates/aggregates.thumb.jpg?v=1788617878Counting and averagingSometimes you do not want the rows, you want a summary of them. An aggregate function does that, and it changes the shape of the answer: five rows go in and…https://exercises.lol/video-media/code_sql_databases/aggregates/aggregates.enzh.mp4?v=17886178781212026-08-23yes https://exercises.lol/videos/code_sql_databases/like-in-between2026-09-05https://exercises.lol/video-media/code_sql_databases/like-in-between/like-in-between.thumb.jpg?v=1788617878LIKE, IN and BETWEENSometimes you do not know the exact value — you know the shape of it. LIKE compares against a pattern. Here are our five students, three times over. Anything…https://exercises.lol/video-media/code_sql_databases/like-in-between/like-in-between.enzh.mp4?v=17886178781232026-08-23yes https://exercises.lol/videos/code_sql_databases/group-by2026-09-05https://exercises.lol/video-media/code_sql_databases/group-by/group-by.thumb.jpg?v=1788617886Grouping with GROUP BYLast lesson an aggregate folded the whole table into one number. Usually you want one number per something — per form, per customer, per month. GROUP BY does…https://exercises.lol/video-media/code_sql_databases/group-by/group-by.enzh.mp4?v=17886178861242026-08-23yes https://exercises.lol/videos/code_sql_databases/keys2026-09-05https://exercises.lol/video-media/code_sql_databases/keys/keys.thumb.jpg?v=1788617965Tables, keys and relationshipsReal databases hold several tables, and the reason is easiest to see by doing it wrong first. Put everything in one table and Ada's name and city are written…https://exercises.lol/video-media/code_sql_databases/keys/keys.enzh.mp4?v=17886179651272026-08-23yes https://exercises.lol/videos/code_sql_databases/inner-join2026-09-05https://exercises.lol/video-media/code_sql_databases/inner-join/inner-join.thumb.jpg?v=1788617957INNER JOINSplitting the data was the right thing to do, but now a question about customers and their orders touches both tables. A join puts them back together, and ON…https://exercises.lol/video-media/code_sql_databases/inner-join/inner-join.enzh.mp4?v=17886179571222026-08-23yes https://exercises.lol/videos/code_sql_databases/join-group2026-09-05https://exercises.lol/video-media/code_sql_databases/join-group/join-group.thumb.jpg?v=1788618001Joins with groupingEverything in this lesson you have already met. A join makes one wide table. GROUP BY sorts that into piles. An aggregate turns each pile into one row each.…https://exercises.lol/video-media/code_sql_databases/join-group/join-group.enzh.mp4?v=17886180011182026-08-23yes https://exercises.lol/videos/code_sql_databases/create-table2026-09-05https://exercises.lol/video-media/code_sql_databases/create-table/create-table.thumb.jpg?v=1788617948Creating tablesSQL splits into two halves, and it is worth being able to name them. DDL, the data definition language, changes the structure — the tables themselves. DML, the…https://exercises.lol/video-media/code_sql_databases/create-table/create-table.enzh.mp4?v=17886179481282026-08-23yes https://exercises.lol/videos/code_sql_databases/alter-drop2026-09-05https://exercises.lol/video-media/code_sql_databases/alter-drop/alter-drop.thumb.jpg?v=1788617974Changing the schemaA table's design is not fixed once it is made. ALTER TABLE ADD gives an existing table a new column, named and typed just as it would have been in the CREATE.…https://exercises.lol/video-media/code_sql_databases/alter-drop/alter-drop.enzh.mp4?v=17886179741132026-08-23yes https://exercises.lol/videos/code_sql_databases/insert2026-09-05https://exercises.lol/video-media/code_sql_databases/insert/insert.thumb.jpg?v=1788617853Inserting rowsINSERT adds a row. Name the table, list the columns you are supplying, and then give the matching values. Run it and the product table has a fourth row — the…https://exercises.lol/video-media/code_sql_databases/insert/insert.enzh.mp4?v=17886178531112026-08-23yes https://exercises.lol/videos/code_sql_databases/update2026-09-05https://exercises.lol/video-media/code_sql_databases/update/update.thumb.jpg?v=1788617985Updating rowsUPDATE changes values in rows that already exist. SET says which column gets which new value, and WHERE says which rows it applies to. Here the WHERE picks the…https://exercises.lol/video-media/code_sql_databases/update/update.enzh.mp4?v=17886179851132026-08-23yes https://exercises.lol/videos/code_sql_databases/delete2026-09-05https://exercises.lol/video-media/code_sql_databases/delete/delete.thumb.jpg?v=1788618006Deleting rowsDELETE removes rows. Name the table and give a WHERE, and that one row goes — the glue, here. Notice the two things that did not happen: the other rows are…https://exercises.lol/video-media/code_sql_databases/delete/delete.enzh.mp4?v=17886180061082026-08-23yes https://exercises.lol/videos/code_sql_databases/normalisation2026-09-05https://exercises.lol/video-media/code_sql_databases/normalisation/normalisation.thumb.jpg?v=1788617867NormalisationPut every club booking in one table and something goes wrong quietly. Look at the coach column: Mr Ng is written twice over, once for each Chess booking. If he…https://exercises.lol/video-media/code_sql_databases/normalisation/normalisation.enzh.mp4?v=17886178671502026-08-23yes https://exercises.lol/videos/code_web_basics/first-page2026-09-05https://exercises.lol/video-media/code_web_basics/first-page/first-page.thumb.jpg?v=1788618213Your first web pageA web page is made with HTML, and HTML is just text — text with tags around it. You write the text on one side, and the browser reads it and draws the page on…https://exercises.lol/video-media/code_web_basics/first-page/first-page.enzh.mp4?v=17886182131302026-08-23yes https://exercises.lol/videos/code_web_basics/headings2026-09-05https://exercises.lol/video-media/code_web_basics/headings/headings.thumb.jpg?v=1788618225HeadingsA heading is a title on your page, and it works exactly like the paragraph you already know: an opening tag, your words, a closing tag. The tag is h one. Press…https://exercises.lol/video-media/code_web_basics/headings/headings.enzh.mp4?v=17886182251402026-08-23yes https://exercises.lol/videos/code_web_basics/emphasis2026-09-05https://exercises.lol/video-media/code_web_basics/emphasis/emphasis.thumb.jpg?v=1788618083Bold, italic, breakUntil now a tag has wrapped a whole block: this line is a paragraph, this line is a heading. Here is something new — a tag that wraps just one word in the…https://exercises.lol/video-media/code_web_basics/emphasis/emphasis.enzh.mp4?v=17886180831262026-08-23yes https://exercises.lol/videos/code_web_basics/lists2026-09-05https://exercises.lol/video-media/code_web_basics/lists/lists.thumb.jpg?v=1788618180ListsA list takes two different tags, and that is the new idea here. The outer one, u l, holds the whole list — it says "a list starts here and ends there". Then…https://exercises.lol/video-media/code_web_basics/lists/lists.enzh.mp4?v=17886181801302026-08-23yes https://exercises.lol/videos/code_web_basics/links2026-09-05https://exercises.lol/video-media/code_web_basics/links/links.thumb.jpg?v=1788618322LinksThe link tag is a, short for anchor, and it brings something genuinely new with it. Inside the opening tag there is extra information: href, followed by an…https://exercises.lol/video-media/code_web_basics/links/links.enzh.mp4?v=17886183221422026-08-23yes https://exercises.lol/videos/code_web_basics/images2026-09-05https://exercises.lol/video-media/code_web_basics/images/images.thumb.jpg?v=1788618299ImagesTo put a picture on a page you use the img tag, and everything it needs lives in its attributes — you met your first one last lesson. Src says which file to…https://exercises.lol/video-media/code_web_basics/images/images.enzh.mp4?v=17886182991362026-08-23yes https://exercises.lol/videos/code_web_basics/real-page2026-09-05https://exercises.lol/video-media/code_web_basics/real-page/real-page.thumb.jpg?v=1788618281A real web pageSo far you have written pieces of a page. A real page puts them in a frame, and it is the same frame on essentially every website in the world, so it is worth…https://exercises.lol/video-media/code_web_basics/real-page/real-page.enzh.mp4?v=17886182811382026-08-23yes https://exercises.lol/videos/code_web_basics/nesting2026-09-05https://exercises.lol/video-media/code_web_basics/nesting/nesting.thumb.jpg?v=1788618259Comments and nestingA comment is a note you leave for yourself inside the file. Open the brackets with an exclamation mark and two dashes, write anything you like, and close it…https://exercises.lol/video-media/code_web_basics/nesting/nesting.enzh.mp4?v=17886182591392026-08-23yes https://exercises.lol/videos/code_web_basics/tables2026-09-05https://exercises.lol/video-media/code_web_basics/tables/tables.thumb.jpg?v=1788618232TablesA table needs three tags nested inside each other, and getting the order right is most of the work. Table wraps the whole thing. Inside it, t r is one row…https://exercises.lol/video-media/code_web_basics/tables/tables.enzh.mp4?v=17886182321292026-08-23yes https://exercises.lol/videos/code_web_basics/forms2026-09-05https://exercises.lol/video-media/code_web_basics/forms/forms.thumb.jpg?v=1788618132FormsEverything you have made so far is something to read. A form is different: it is something a visitor uses. Write an input with type text and you get a real box…https://exercises.lol/video-media/code_web_basics/forms/forms.enzh.mp4?v=17886181321272026-08-23yes https://exercises.lol/videos/code_web_basics/sections2026-09-05https://exercises.lol/video-media/code_web_basics/sections/sections.thumb.jpg?v=1788618317Sections and classesSmall pages are fine as one stack of tags. Bigger ones are not — a visitor sees a title, then the content, then a note at the bottom, and if your HTML is just…https://exercises.lol/video-media/code_web_basics/sections/sections.enzh.mp4?v=17886183171382026-08-23yes https://exercises.lol/videos/code_web_basics/first-css2026-09-05https://exercises.lol/video-media/code_web_basics/first-css/first-css.thumb.jpg?v=1788618140Your first CSSHalfway through the course, a second language arrives. HTML says what each thing IS — this is a paragraph, that is a heading. CSS says how it looks — this…https://exercises.lol/video-media/code_web_basics/first-css/first-css.enzh.mp4?v=17886181401402026-08-23yes https://exercises.lol/videos/code_web_basics/selectors2026-09-05https://exercises.lol/video-media/code_web_basics/selectors/selectors.thumb.jpg?v=1788618130SelectorsLast lesson your selector was a tag name, which changes every paragraph on the page. That is often too many. So there are two more. Write a name with a dot in…https://exercises.lol/video-media/code_web_basics/selectors/selectors.enzh.mp4?v=17886181301372026-08-23yes https://exercises.lol/videos/code_web_basics/colours2026-09-05https://exercises.lol/video-media/code_web_basics/colours/colours.thumb.jpg?v=1788618135ColoursThe simplest way to write a colour is to name it. Red and blue you would expect; there are also tomato, gold, teal, steel blue, orchid — about a hundred and…https://exercises.lol/video-media/code_web_basics/colours/colours.enzh.mp4?v=17886181351312026-08-23yes https://exercises.lol/videos/code_web_basics/text-style2026-09-05https://exercises.lol/video-media/code_web_basics/text-style/text-style.thumb.jpg?v=1788618218Styling textBack in lesson two the browser chose your heading sizes for you. Now you can choose them yourself, with font-size, measured in pixels. Forty pixels for a…https://exercises.lol/video-media/code_web_basics/text-style/text-style.enzh.mp4?v=17886182181352026-08-23yes https://exercises.lol/videos/code_web_basics/box-model2026-09-05https://exercises.lol/video-media/code_web_basics/box-model/box-model.thumb.jpg?v=1788618311The box modelCSS treats every single element as a box, and every box has four layers. In the middle is the content — your text or your picture. Around that is padding…https://exercises.lol/video-media/code_web_basics/box-model/box-model.enzh.mp4?v=17886183111382026-08-23yes https://exercises.lol/videos/code_web_basics/spacing2026-09-05https://exercises.lol/video-media/code_web_basics/spacing/spacing.thumb.jpg?v=1788618154MarginMargin is the space outside a box, and here is the thing about it: on a box with nothing around it, a margin changes nothing you can see. Put two boxes…https://exercises.lol/video-media/code_web_basics/spacing/spacing.enzh.mp4?v=17886181541362026-08-23yes https://exercises.lol/videos/code_web_basics/display2026-09-05https://exercises.lol/video-media/code_web_basics/display/display.thumb.jpg?v=1788618205displayYou have been watching this since lesson three without a name for it. Some elements take a whole line to themselves and stretch across the page: a div, a…https://exercises.lol/video-media/code_web_basics/display/display.enzh.mp4?v=17886182051362026-08-23yes https://exercises.lol/videos/code_web_basics/width2026-09-05https://exercises.lol/video-media/code_web_basics/width/width.thumb.jpg?v=1788618134Width and centeringHere is something you may not have noticed: a block box is already as wide as the page. It has been all along — you just could not see the edges without a…https://exercises.lol/video-media/code_web_basics/width/width.enzh.mp4?v=17886181341282026-08-23yes https://exercises.lol/videos/code_web_basics/flexbox2026-09-05https://exercises.lol/video-media/code_web_basics/flexbox/flexbox.thumb.jpg?v=1788618251FlexboxEverything you have built so far stacks downward, because that is what block boxes do. But a navigation bar, a row of cards, a toolbar — those need to sit…https://exercises.lol/video-media/code_web_basics/flexbox/flexbox.enzh.mp4?v=17886182511172026-08-23yes https://exercises.lol/videos/code_web_basics/profile-card2026-09-05https://exercises.lol/video-media/code_web_basics/profile-card/profile-card.thumb.jpg?v=1788618103Your profile cardLast lesson, and it is a project rather than a new idea. You are building a profile card: a picture at the top, a name in a colour you choose, and one line…https://exercises.lol/video-media/code_web_basics/profile-card/profile-card.enzh.mp4?v=17886181031392026-08-23yes https://exercises.lol/videos/igcse_biology/classification2026-09-03https://exercises.lol/video-media/igcse_biology/classification/classification.thumb.jpg?v=1788417487Characteristics & ClassificationA car moves. It uses fuel, gives off waste gases, and responds when you turn the wheel. So is a car alive? No — and biology can tell you exactly why. Living…https://exercises.lol/video-media/igcse_biology/classification/classification.enzh.mp4?v=17884174879022026-08-15yes https://exercises.lol/videos/igcse_biology/cells2026-09-03https://exercises.lol/video-media/igcse_biology/cells/cells.thumb.jpg?v=1788417400Cell StructureZoom in on a leaf, on your skin, on a drop of pond water — and you find the same thing everywhere: cells. A cell is the smallest thing that can carry out all…https://exercises.lol/video-media/igcse_biology/cells/cells.enzh.mp4?v=17884174008202026-08-15yes https://exercises.lol/videos/igcse_biology/transport-in-cells2026-09-05https://exercises.lol/video-media/igcse_biology/transport-in-cells/transport-in-cells.thumb.jpg?v=1788573727Movement Into and Out of CellsA cell is surrounded by a membrane, and it must keep trading with the world outside. Oxygen has to get in. Carbon dioxide has to get out. Water moves both…https://exercises.lol/video-media/igcse_biology/transport-in-cells/transport-in-cells.enzh.mp4?v=17885737274642026-08-15yes https://exercises.lol/videos/igcse_biology/biological-molecules2026-09-03https://exercises.lol/video-media/igcse_biology/biological-molecules/biological-molecules.thumb.jpg?v=1788438439Biological MoleculesBread, meat, oil, your own muscles — all of them are built from just a handful of chemical elements. And the large molecules in your food are not really large…https://exercises.lol/video-media/igcse_biology/biological-molecules/biological-molecules.enzh.mp4?v=17884384393252026-08-15yes https://exercises.lol/videos/igcse_biology/enzymes2026-09-03https://exercises.lol/video-media/igcse_biology/enzymes/enzymes.thumb.jpg?v=1788439604EnzymesEvery second, thousands of chemical reactions are running inside you. Left to themselves, almost all of them would be far too slow to keep you alive. What…https://exercises.lol/video-media/igcse_biology/enzymes/enzymes.enzh.mp4?v=17884396043542026-08-15yes https://exercises.lol/videos/igcse_biology/photosynthesis2026-09-05https://exercises.lol/video-media/igcse_biology/photosynthesis/photosynthesis.thumb.jpg?v=1788574027PhotosynthesisA plant cannot hunt and it cannot move. So it builds its own food out of almost nothing: a gas from the air, water from the soil, and light. Every meal you…https://exercises.lol/video-media/igcse_biology/photosynthesis/photosynthesis.enzh.mp4?v=17885740274552026-08-15yes https://exercises.lol/videos/igcse_biology/human-nutrition2026-09-03https://exercises.lol/video-media/igcse_biology/human-nutrition/human-nutrition.thumb.jpg?v=1788452040Human NutritionThe food on your plate is made of molecules far too big to enter your blood. So your body takes it apart — first by crushing it, then by cutting the molecules…https://exercises.lol/video-media/igcse_biology/human-nutrition/human-nutrition.enzh.mp4?v=17884520409522026-08-15yes https://exercises.lol/videos/igcse_biology/transport-in-plants2026-09-03https://exercises.lol/video-media/igcse_biology/transport-in-plants/transport-in-plants.thumb.jpg?v=1788439946Transport in PlantsA tall tree lifts water a hundred metres into the air, every day, with no pump and no moving parts. It does it using nothing but evaporation from its leaves…https://exercises.lol/video-media/igcse_biology/transport-in-plants/transport-in-plants.enzh.mp4?v=17884399463542026-08-15yes https://exercises.lol/videos/igcse_biology/circulation2026-09-03https://exercises.lol/video-media/igcse_biology/circulation/circulation.thumb.jpg?v=1788438822Transport in AnimalsYour heart beats about a hundred thousand times a day, and it has never once stopped to rest. It is not really one pump — it is two, side by side, sharing a…https://exercises.lol/video-media/igcse_biology/circulation/circulation.enzh.mp4?v=17884388225012026-08-15yes https://exercises.lol/videos/igcse_biology/disease-immunity2026-09-03https://exercises.lol/video-media/igcse_biology/disease-immunity/disease-immunity.thumb.jpg?v=1788437319Diseases and ImmunityRight now, your body is being tested by microbes — on your skin, in the air you breathe, in the food you eat. Almost all of them never get in. And when one…https://exercises.lol/video-media/igcse_biology/disease-immunity/disease-immunity.enzh.mp4?v=17884373193642026-08-15yes https://exercises.lol/videos/igcse_biology/gas-exchange2026-09-03https://exercises.lol/video-media/igcse_biology/gas-exchange/gas-exchange.thumb.jpg?v=1788439522Gas Exchange in HumansYour lungs would cover half a tennis court if you spread them flat. They are not one big bag — they are millions of tiny sacs, and that is the whole point.…https://exercises.lol/video-media/igcse_biology/gas-exchange/gas-exchange.enzh.mp4?v=17884395223532026-08-15yes https://exercises.lol/videos/igcse_biology/respiration2026-09-03https://exercises.lol/video-media/igcse_biology/respiration/respiration.thumb.jpg?v=1788446245RespirationHere is the single most common mix-up in IGCSE Biology. Respiration is not breathing. Breathing is moving air in and out of your lungs — a physical action…https://exercises.lol/video-media/igcse_biology/respiration/respiration.enzh.mp4?v=17884462452992026-08-15yes https://exercises.lol/videos/igcse_biology/excretion2026-09-03https://exercises.lol/video-media/igcse_biology/excretion/excretion.thumb.jpg?v=1788445355Excretion in HumansYour kidneys filter your entire blood supply about thirty times a day. But here is the clever part: they do not pick out the rubbish. They throw almost…https://exercises.lol/video-media/igcse_biology/excretion/excretion.enzh.mp4?v=17884453552902026-08-15yes https://exercises.lol/videos/igcse_biology/coordination2026-09-03https://exercises.lol/video-media/igcse_biology/coordination/coordination.thumb.jpg?v=1788443557Coordination and ResponseTouch something hot and your hand is already moving before you feel the pain. That is one of your two control systems — the fast one, made of nerves. The other…https://exercises.lol/video-media/igcse_biology/coordination/coordination.enzh.mp4?v=178844355710932026-08-15yes https://exercises.lol/videos/igcse_biology/drugs2026-09-05https://exercises.lol/video-media/igcse_biology/drugs/drugs.thumb.jpg?v=1788572318Drugs and AntibioticsAsk a doctor for antibiotics when you have a cold and they will say no. Not because they are being difficult — because it genuinely would not work, and because…https://exercises.lol/video-media/igcse_biology/drugs/drugs.enzh.mp4?v=17885723182762026-08-15yes https://exercises.lol/videos/igcse_biology/reproduction2026-09-03https://exercises.lol/video-media/igcse_biology/reproduction/reproduction.thumb.jpg?v=1788440213ReproductionThere are only two ways to make a new organism, and they trade off against each other. One is fast, needs a single parent, and makes perfect copies. The other…https://exercises.lol/video-media/igcse_biology/reproduction/reproduction.enzh.mp4?v=17884402136392026-08-15yes https://exercises.lol/videos/igcse_biology/inheritance2026-09-03https://exercises.lol/video-media/igcse_biology/inheritance/inheritance.thumb.jpg?v=1788417613InheritanceTwo brown-eyed parents can have a blue-eyed child. That is not a mistake, and it is not a surprise once you can read genotypes. By the end of this lesson you…https://exercises.lol/video-media/igcse_biology/inheritance/inheritance.enzh.mp4?v=17884176134902026-08-15yes https://exercises.lol/videos/igcse_biology/variation-selection2026-09-05https://exercises.lol/video-media/igcse_biology/variation-selection/variation-selection.thumb.jpg?v=1788573298Variation and selectionIn the year eighteen hundred, almost every peppered moth in England was pale. Fifty years later, in the smoky cities, almost every one was black. No moth…https://exercises.lol/video-media/igcse_biology/variation-selection/variation-selection.enzh.mp4?v=17885732984552026-08-15yes https://exercises.lol/videos/igcse_biology/organisms-and-their-environment2026-09-03https://exercises.lol/video-media/igcse_biology/organisms-and-their-environment/organisms-and-their-environment.thumb.jpg?v=1788417626Organisms and their EnvironmentAn African savanna. A coral reef. They look nothing alike, but they run on the same rule. Every living thing here is joined to the others by feeding. Energy…https://exercises.lol/video-media/igcse_biology/organisms-and-their-environment/organisms-and-their-environment.enzh.mp4?v=17884176264912026-08-15yes https://exercises.lol/videos/igcse_biology/human-influences-on-ecosystems2026-09-03https://exercises.lol/video-media/igcse_biology/human-influences-on-ecosystems/human-influences-on-ecosystems.thumb.jpg?v=1788440015Human influences on ecosystemsA farmer spreads fertiliser on a field. Ordinary, useful work. Two kilometres away there is a river, full of fish. Three weeks later those fish are floating…https://exercises.lol/video-media/igcse_biology/human-influences-on-ecosystems/human-influences-on-ecosystems.enzh.mp4?v=17884400154632026-08-15yes https://exercises.lol/videos/igcse_biology/biotechnology-and-genetic-modification2026-09-05https://exercises.lol/video-media/igcse_biology/biotechnology-and-genetic-modification/biotechnology-and-genetic-modification.thumb.jpg?v=1788567978Biotechnology and genetic modificationSteel tanks, warm and gently stirred. Inside tanks like these, billions of living microbes are working for us — making penicillin, a protein food called…https://exercises.lol/video-media/igcse_biology/biotechnology-and-genetic-modification/biotechnology-and-genetic-modification.enzh.mp4?v=17885679784782026-08-15yes https://exercises.lol/videos/igcse_business_studies/understanding-business-activity2026-09-03https://exercises.lol/video-media/igcse_business_studies/understanding-business-activity/understanding-business-activity.thumb.jpg?v=1788451324Understanding business activityLook at any high street. Shop after shop, all selling something, all chasing the same customers. Every one of them is a business. But what is a business really…https://exercises.lol/video-media/igcse_business_studies/understanding-business-activity/understanding-business-activity.enzh.mp4?v=178845132410712026-08-15yes https://exercises.lol/videos/igcse_business_studies/people-in-business2026-09-03https://exercises.lol/video-media/igcse_business_studies/people-in-business/people-in-business.thumb.jpg?v=1788450933People in businessLook at this factory floor. Hundreds of people, side by side, each doing a small part of one job. Every one of them had to be found, trained, paid — and given…https://exercises.lol/video-media/igcse_business_studies/people-in-business/people-in-business.enzh.mp4?v=17884509337912026-08-15yes https://exercises.lol/videos/igcse_business_studies/marketing2026-09-03https://exercises.lol/video-media/igcse_business_studies/marketing/marketing.thumb.jpg?v=1788441551MarketingCount the messages in this one street. Screens, posters, logos — every one of them is a business trying to reach you. But adverts are only the last step. Long…https://exercises.lol/video-media/igcse_business_studies/marketing/marketing.enzh.mp4?v=17884415515482026-08-15yes https://exercises.lol/videos/igcse_business_studies/operations-management2026-09-03https://exercises.lol/video-media/igcse_business_studies/operations-management/operations-management.thumb.jpg?v=1788437298Operations managementLook inside a car factory. The same car, again and again, hundreds every day, each one exactly like the last. Somebody decided all of it: how to make it, what…https://exercises.lol/video-media/igcse_business_studies/operations-management/operations-management.enzh.mp4?v=17884372985862026-08-15yes https://exercises.lol/videos/igcse_business_studies/financial-information-and-decisions2026-09-03https://exercises.lol/video-media/igcse_business_studies/financial-information-and-decisions/financial-information-and-decisions.thumb.jpg?v=1788450745Financial information and decisionsThis business was doing well. Every month it made a profit — the products sold, the customers were happy. But watch the money in the bank. Suppliers wanted…https://exercises.lol/video-media/igcse_business_studies/financial-information-and-decisions/financial-information-and-decisions.enzh.mp4?v=17884507457722026-08-15yes https://exercises.lol/videos/igcse_business_studies/external-influences-on-business2026-09-03https://exercises.lol/video-media/igcse_business_studies/external-influences-on-business/external-influences-on-business.thumb.jpg?v=1788451280External influences on business activityThis building is not a business. Nobody inside it sells anything. But the people in there can raise a tax, change a law, or push interest rates up — and every…https://exercises.lol/video-media/igcse_business_studies/external-influences-on-business/external-influences-on-business.enzh.mp4?v=17884512805032026-08-15yes https://exercises.lol/videos/igcse_chemistry/states-of-matter2026-09-05https://exercises.lol/video-media/igcse_chemistry/states-of-matter/states-of-matter.thumb.jpg?v=1788570918States of MatterSit in a room while someone makes coffee next door. Soon you can smell it, even from across the room. How? Everything around you is made of tiny particles, far…https://exercises.lol/video-media/igcse_chemistry/states-of-matter/states-of-matter.enzh.mp4?v=17885709188122026-08-15yes https://exercises.lol/videos/igcse_chemistry/atoms-bonding2026-09-05https://exercises.lol/video-media/igcse_chemistry/atoms-bonding/atoms-bonding.thumb.jpg?v=1788574313Atoms & BondingLook at these two things. A diamond — the hardest material you can buy. And the soft, grey lead in a pencil. They could not seem more different. Yet both are…https://exercises.lol/video-media/igcse_chemistry/atoms-bonding/atoms-bonding.enzh.mp4?v=178857431310022026-08-15yes https://exercises.lol/videos/igcse_chemistry/stoichiometry2026-09-05https://exercises.lol/video-media/igcse_chemistry/stoichiometry/stoichiometry.thumb.jpg?v=1788573211StoichiometryHere is a chemist's problem. A single atom is far too small to see, and there are billions upon billions in the tiniest speck. So how do you count them? You…https://exercises.lol/video-media/igcse_chemistry/stoichiometry/stoichiometry.enzh.mp4?v=17885732119322026-08-15yes https://exercises.lol/videos/igcse_chemistry/electrolysis2026-09-05https://exercises.lol/video-media/igcse_chemistry/electrolysis/electrolysis.thumb.jpg?v=1788573751ElectrolysisElectricity can do something amazing: it can tear a compound apart. Pass a current through a melted or dissolved compound, and it splits into its elements.…https://exercises.lol/video-media/igcse_chemistry/electrolysis/electrolysis.enzh.mp4?v=17885737516242026-08-15yes https://exercises.lol/videos/igcse_chemistry/energetics2026-09-05https://exercises.lol/video-media/igcse_chemistry/energetics/energetics.thumb.jpg?v=1788575165EnergeticsSnap a glow stick, and it lights up. Hold a hand-warmer, and it gets hot. Open an instant cold pack, and it turns icy. In every case, a chemical reaction is…https://exercises.lol/video-media/igcse_chemistry/energetics/energetics.enzh.mp4?v=17885751653502026-08-15yes https://exercises.lol/videos/igcse_chemistry/rates-equilibrium2026-09-03https://exercises.lol/video-media/igcse_chemistry/rates-equilibrium/rates-equilibrium.thumb.jpg?v=1788449275Rates & EquilibriumMilk on the counter spoils in a day. In the fridge, it lasts a week. Same milk — but the reaction runs at a different speed. First, a quick check: a chemical…https://exercises.lol/video-media/igcse_chemistry/rates-equilibrium/rates-equilibrium.enzh.mp4?v=17884492759532026-08-15yes https://exercises.lol/videos/igcse_chemistry/acids-bases-salts2026-09-05https://exercises.lol/video-media/igcse_chemistry/acids-bases-salts/acids-bases-salts.thumb.jpg?v=1788574960Acids, Bases & SaltsLemon juice, vinegar, and the acid in your stomach — acids are everywhere. So are their opposites: alkalis, like soap and oven cleaner. Mix an acid and an…https://exercises.lol/video-media/igcse_chemistry/acids-bases-salts/acids-bases-salts.enzh.mp4?v=17885749607862026-08-15yes https://exercises.lol/videos/igcse_chemistry/periodic-table2026-09-03https://exercises.lol/video-media/igcse_chemistry/periodic-table/periodic-table.thumb.jpg?v=1788453537The Periodic TableThis is the most powerful chart in all of chemistry: the Periodic Table. It looks like a jumble of boxes, but it hides a beautiful secret. The elements are…https://exercises.lol/video-media/igcse_chemistry/periodic-table/periodic-table.enzh.mp4?v=17884535376742026-08-15yes https://exercises.lol/videos/igcse_chemistry/metals2026-09-05https://exercises.lol/video-media/igcse_chemistry/metals/metals.thumb.jpg?v=1788574423MetalsWhy do we dig gold out of the ground as shiny nuggets, but iron only as dull, rusty rock? And why does a soda can never rust, while an iron nail does? The…https://exercises.lol/video-media/igcse_chemistry/metals/metals.enzh.mp4?v=17885744238222026-08-15yes https://exercises.lol/videos/igcse_chemistry/environment2026-09-05https://exercises.lol/video-media/igcse_chemistry/environment/environment.thumb.jpg?v=1788575161Chemistry of the EnvironmentLook at a glass of water, and the air in this room. Both look clean and simple. But natural water carries dissolved oxygen, minerals, and sometimes sewage and…https://exercises.lol/video-media/igcse_chemistry/environment/environment.enzh.mp4?v=17885751616362026-08-15yes https://exercises.lol/videos/igcse_chemistry/organic2026-09-05https://exercises.lol/video-media/igcse_chemistry/organic/organic.thumb.jpg?v=1788570928Organic ChemistryPetrol, plastic bottles, vinegar, alcohol, and the proteins in your body. They seem completely unrelated. But every one of them is built from carbon. Carbon is…https://exercises.lol/video-media/igcse_chemistry/organic/organic.enzh.mp4?v=178857092810102026-08-15yes https://exercises.lol/videos/igcse_chemistry/experimental2026-09-03https://exercises.lol/video-media/igcse_chemistry/experimental/experimental.thumb.jpg?v=1788450841Experimental TechniquesYou are handed an unknown white powder and a colourless solution. No labels. How do you find out what they are? Chemistry gives you a detective's toolkit: add…https://exercises.lol/video-media/igcse_chemistry/experimental/experimental.enzh.mp4?v=17884508418062026-08-15yes https://exercises.lol/videos/igcse_computer_science/binary2026-09-05https://exercises.lol/video-media/igcse_computer_science/binary/binary.thumb.jpg?v=1788568581Why Computers Use BinaryInside a processor there are billions of tiny switches. Each one can only be on, or off. That is all a computer physically has — no threes, no sevens, no…https://exercises.lol/video-media/igcse_computer_science/binary/binary.enzh.mp4?v=178856858112752026-08-15yes https://exercises.lol/videos/igcse_computer_science/data-transmission2026-09-03https://exercises.lol/video-media/igcse_computer_science/data-transmission/data-transmission.thumb.jpg?v=1788440370Data TransmissionYou send a photo to a friend on the other side of the world. It does not travel as one lump. It is chopped into hundreds of small packets, each one labelled…https://exercises.lol/video-media/igcse_computer_science/data-transmission/data-transmission.enzh.mp4?v=17884403706552026-08-15yes https://exercises.lol/videos/igcse_computer_science/cpu2026-09-05https://exercises.lol/video-media/igcse_computer_science/cpu/cpu.thumb.jpg?v=1788568728The CPUThe processor in your phone is doing something almost stupidly simple. Fetch one instruction. Work out what it means. Do it. Then fetch the next one. That is…https://exercises.lol/video-media/igcse_computer_science/cpu/cpu.enzh.mp4?v=178856872810852026-08-15yes https://exercises.lol/videos/igcse_computer_science/hardware-software2026-09-03https://exercises.lol/video-media/igcse_computer_science/hardware-software/hardware-software.thumb.jpg?v=1788446173Hardware & SoftwareHere is a brand new computer. Every physical part works — the processor, the memory, the screen, the keyboard. Switch it on, and nothing happens. No desktop…https://exercises.lol/video-media/igcse_computer_science/hardware-software/hardware-software.enzh.mp4?v=17884461737882026-08-15yes https://exercises.lol/videos/igcse_computer_science/internet-web2026-09-05https://exercises.lol/video-media/igcse_computer_science/internet-web/internet-web.thumb.jpg?v=1788569115The Internet & the WebYou type a web address and press enter. Less than a second later, a page appears — a page that lives on a computer maybe ten thousand kilometres away. In that…https://exercises.lol/video-media/igcse_computer_science/internet-web/internet-web.enzh.mp4?v=17885691155892026-08-15yes https://exercises.lol/videos/igcse_computer_science/automated-systems2026-09-05https://exercises.lol/video-media/igcse_computer_science/automated-systems/automated-systems.thumb.jpg?v=1788567415Automated SystemsPicture a greenhouse at three in the morning. Nobody is there. The air warms up a little, and a window slides open all by itself. An hour later it closes…https://exercises.lol/video-media/igcse_computer_science/automated-systems/automated-systems.enzh.mp4?v=17885674156212026-08-15yes https://exercises.lol/videos/igcse_computer_science/program-development-life-cycle2026-09-05https://exercises.lol/video-media/igcse_computer_science/program-development-life-cycle/program-development-life-cycle.thumb.jpg?v=1788567610The Program Development Life CycleEvery app on your phone was written by someone like this. But they did not start by typing code. Before the first line, the problem was studied, the solution…https://exercises.lol/video-media/igcse_computer_science/program-development-life-cycle/program-development-life-cycle.enzh.mp4?v=17885676105572026-08-15yes https://exercises.lol/videos/igcse_computer_science/programming2026-09-05https://exercises.lol/video-media/igcse_computer_science/programming/programming.thumb.jpg?v=1788568856ProgrammingHere is a short program. It reads five test marks and prints the total. The five marks are eight, nine, seven, six and ten, so the total should be forty. Watch…https://exercises.lol/video-media/igcse_computer_science/programming/programming.enzh.mp4?v=17885688567962026-08-15yes https://exercises.lol/videos/igcse_computer_science/databases2026-09-05https://exercises.lol/video-media/igcse_computer_science/databases/databases.thumb.jpg?v=1788567554DatabasesBefore computers, a library kept a drawer like this. One card per book, each holding the same few facts, all kept in order — so a librarian could find any book…https://exercises.lol/video-media/igcse_computer_science/databases/databases.enzh.mp4?v=17885675544972026-08-15yes https://exercises.lol/videos/igcse_computer_science/boolean-logic2026-09-05https://exercises.lol/video-media/igcse_computer_science/boolean-logic/boolean-logic.thumb.jpg?v=1788567352Boolean LogicLook closely at this chip. There is nothing clever inside it. It cannot think. Inside are millions of tiny switches, and each switch can only be one of two…https://exercises.lol/video-media/igcse_computer_science/boolean-logic/boolean-logic.enzh.mp4?v=17885673525172026-08-15yes https://exercises.lol/videos/igcse_economics/basic-economic-problem2026-09-05https://exercises.lol/video-media/igcse_economics/basic-economic-problem/basic-economic-problem.thumb.jpg?v=1788575377The Basic Economic ProblemYou have ten dollars. In front of you there is a book you want and a game you want. You want both. You can only have one. So you pick the book — and the moment…https://exercises.lol/video-media/igcse_economics/basic-economic-problem/basic-economic-problem.enzh.mp4?v=17885753775542026-08-15yes https://exercises.lol/videos/igcse_economics/allocation-of-resources2026-09-05https://exercises.lol/video-media/igcse_economics/allocation-of-resources/allocation-of-resources.thumb.jpg?v=1788573169The Allocation of ResourcesNobody in the world is in charge of deciding how many coffee beans to grow. No committee meets. No plan is written. And yet, most mornings, there is coffee.…https://exercises.lol/video-media/igcse_economics/allocation-of-resources/allocation-of-resources.enzh.mp4?v=178857316913102026-08-15yes https://exercises.lol/videos/igcse_economics/microeconomic-decision-makers2026-09-05https://exercises.lol/video-media/igcse_economics/microeconomic-decision-makers/microeconomic-decision-makers.thumb.jpg?v=1788573342Microeconomic Decision-MakersYou have a fish. You want a pair of shoes. Long ago that meant barter — swapping goods directly. And to do it, you need to find someone who has shoes, and who…https://exercises.lol/video-media/igcse_economics/microeconomic-decision-makers/microeconomic-decision-makers.enzh.mp4?v=17885733427582026-08-15yes https://exercises.lol/videos/igcse_economics/government-and-the-macroeconomy2026-09-05https://exercises.lol/video-media/igcse_economics/government-and-the-macroeconomy/government-and-the-macroeconomy.thumb.jpg?v=1788573694Government and the MacroeconomyImagine you are the government. You want the economy to grow faster. So you spend more, firms hire, and unemployment falls. Excellent. Then prices start…https://exercises.lol/video-media/igcse_economics/government-and-the-macroeconomy/government-and-the-macroeconomy.enzh.mp4?v=17885736947272026-08-15yes https://exercises.lol/videos/igcse_economics/economic-development2026-09-05https://exercises.lol/video-media/igcse_economics/economic-development/economic-development.thumb.jpg?v=1788574379Economic developmentTwo babies are born on the same morning. One in a rich country, one in a poor country. Neither of them chose where. Yet one will probably live many years…https://exercises.lol/video-media/igcse_economics/economic-development/economic-development.enzh.mp4?v=17885743795232026-08-15yes https://exercises.lol/videos/igcse_economics/international-trade-and-globalisation2026-09-05https://exercises.lol/video-media/igcse_economics/international-trade-and-globalisation/international-trade-and-globalisation.thumb.jpg?v=1788574444International trade and globalisationLook around your room. The phone in your hand, the coffee in your cup, the clothes you are wearing — almost none of it was made here. It came by sea, in steel…https://exercises.lol/video-media/igcse_economics/international-trade-and-globalisation/international-trade-and-globalisation.enzh.mp4?v=17885744445382026-08-15yes https://exercises.lol/videos/igcse_mathematics/geometry2026-09-05https://exercises.lol/video-media/igcse_mathematics/geometry/geometry.thumb.jpg?v=1788584843GeometryLook closely at a honeycomb. Every cell is a hexagon — six straight sides, all the same. Not squares. Not pentagons. Hexagons. Bees never studied geometry, but…https://exercises.lol/video-media/igcse_mathematics/geometry/geometry.enzh.mp4?v=17885848438042026-08-15yes https://exercises.lol/videos/igcse_mathematics/mensuration2026-09-05https://exercises.lol/video-media/igcse_mathematics/mensuration/mensuration.thumb.jpg?v=1788585009MensurationThe Great Pyramid of Giza has stood for four and a half thousand years. How much stone is inside it? About two and a half million cubic metres — and one…https://exercises.lol/video-media/igcse_mathematics/mensuration/mensuration.enzh.mp4?v=17885850094672026-08-15yes https://exercises.lol/videos/igcse_physics/motion-forces-energy2026-09-05https://exercises.lol/video-media/igcse_physics/motion-forces-energy/motion-forces-energy.thumb.jpg?v=1788588017Motion, Forces & EnergyLook around you. A car speeds up. A ball drops. A cup sits still on a table. Physics can describe every one of these — exactly, using numbers. And it all rests…https://exercises.lol/video-media/igcse_physics/motion-forces-energy/motion-forces-energy.enzh.mp4?v=178858801713202026-08-15yes https://exercises.lol/videos/igcse_physics/thermal-physics2026-09-05https://exercises.lol/video-media/igcse_physics/thermal-physics/thermal-physics.thumb.jpg?v=1788584794Thermal PhysicsWhat is heat, really? Zoom in far enough, and everything is made of tiny particles, always moving. Heat something, and its particles move faster. Cool it, and…https://exercises.lol/video-media/igcse_physics/thermal-physics/thermal-physics.enzh.mp4?v=17885847947122026-08-15yes https://exercises.lol/videos/igcse_physics/nuclear-physics2026-09-05https://exercises.lol/video-media/igcse_physics/nuclear-physics/nuclear-physics.thumb.jpg?v=1788584345Nuclear PhysicsEverything around you is made of atoms — yet an atom is almost entirely empty space. If the nucleus were the size of a marble, the whole atom would be the size…https://exercises.lol/video-media/igcse_physics/nuclear-physics/nuclear-physics.enzh.mp4?v=17885843459462026-08-15yes https://exercises.lol/videos/igcse_physics/space-physics2026-09-05https://exercises.lol/video-media/igcse_physics/space-physics/space-physics.thumb.jpg?v=1788584818Space PhysicsLook up on a clear night, and you might see a few thousand stars. But that is almost nothing. Our Sun is just one star among a hundred billion in our galaxy…https://exercises.lol/video-media/igcse_physics/space-physics/space-physics.enzh.mp4?v=178858481810192026-08-15yes