— 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 a generic Archimedes buoyancy demo (sphere + sliders) but completely misses the required two-crown (pure gold vs. gilded) scenario, vertical immersion slider, fall/splash animations, and Heureka moment.