— Two crowns — Same mass, different density — Vertical slider — Slider works — Slider controls crowns — Slider direction correct — Full slider range — Fall animation — Water displacement — Rising water level — Splash effects ✓ Physics correct ✓ Live mass value ✓ Live volume value ✓ Live density value ✓ Live displaced water — Gilded displaces more — Heureka animation ✓ No external deps — Light bg / dark text ✓ Self-contained HTML
Completely misses the prompt's core requirements (two crowns, vertical crown-dipping slider, fall/splash animations, Heureka moment) — instead delivers a generic Archimedes buoyancy sandbox with no crown context whatsoever.