— 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
Implements generic Archimedes buoyancy (single ellipse object, auto-play button animation) but entirely omits the two-crown scenario, vertical slider, Heureka moment, splash effects, and all four required live values (mass, volume, density, displaced water).