/* radioactive_decay.css — the nuclei grid drawn by viz/radioactive_decay.js. */

.rd-nuc { stroke-width: 1; transition: fill 0.18s ease; }
.rd-alive { fill: #fb923c; stroke: #7c3a10; }     /* still radioactive — warm */
.rd-gone { fill: #334155; stroke: #1e293b; }      /* decayed to a stable nucleus — grey */