✓ 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
Slider direction is inverted (value=0 at top means crowns in air, but HTML range inputs render min at bottom when vertical, so dragging up increases value and submerges crowns — semantically backwards); no smooth fall animation (crowns teleport with slider, no keyframe drop); splash exists but only flickers in a narrow threshold window making it rarely visible in practice.
Slider direction is inverted (value=0 at top means crowns in air, but HTML range inputs render min at bottom when vertical, so dragging up increases value and submerges crowns — semantically backwards); no smooth fall animation (crowns teleport with slider, no keyframe drop); splash exists but only flickers in a narrow threshold window making it rarely visible in practice.