✓ 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 crowns to air correctly via CSS `writing-mode: bt-lr`, but native range behavior with vertical orientation is browser-inconsistent and the slider thumb starts at top=0% which should mean crowns in air — functionally it may work, but the crown entry threshold at 30% creates a dead zone and the gilded crown is shown as silver-density rather than a gold-silver alloy, which is a minor physical simplification.
Slider direction is inverted (min=0 at top maps crowns to air correctly via CSS `writing-mode: bt-lr`, but native range behavior with vertical orientation is browser-inconsistent and the slider thumb starts at top=0% which should mean crowns in air — functionally it may work, but the crown entry threshold at 30% creates a dead zone and the gilded crown is shown as silver-density rather than a gold-silver alloy, which is a minor physical simplification.