✓ 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 (label says "up to submerge" but writing-mode bt-lr means dragging up increases value, yet the UI labels place "Luft" at top and "Wasser" at bottom — semantically backwards from spec); crown positions update only on slider 'input' events rather than continuously in the animation loop, causing crowns to freeze mid-animation after release.
Slider direction is inverted (label says "up to submerge" but writing-mode bt-lr means dragging up increases value, yet the UI labels place "Luft" at top and "Wasser" at bottom — semantically backwards from spec); crown positions update only on slider 'input' events rather than continuously in the animation loop, causing crowns to freeze mid-animation after release.