✓ 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 (min=0 at top maps to air, but the HTML vertical range's visual top is its max, so the crown submerges when dragging toward the visually-top position), gilded crown uses copper density (8.9 g/cm³) rather than a realistic gold-alloy value (~11–14 g/cm³), and the submerge calculation anchors crowns far above the container so they never realistically reach the water baseline at slider=100.
Slider direction is inverted (min=0 at top maps to air, but the HTML vertical range's visual top is its max, so the crown submerges when dragging toward the visually-top position), gilded crown uses copper density (8.9 g/cm³) rather than a realistic gold-alloy value (~11–14 g/cm³), and the submerge calculation anchors crowns far above the container so they never realistically reach the water baseline at slider=100.