— 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, Archimedes' crown story, vertical slider): instead shows a generic single-object buoyancy demo with horizontal sliders, wrong physics units, and no crown-specific logic.