✓ 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 top=air/bottom=water, but the range input's bt-lr writing-mode with value=0 starts at bottom, so dragging up increases value and submerges crowns, making top=water semantically); otherwise an exceptionally complete and polished implementation with correct physics, particle splashes, buoyancy arrows, live info panels, and a full Heureka overlay with confetti.
Slider direction is inverted (label says top=air/bottom=water, but the range input's bt-lr writing-mode with value=0 starts at bottom, so dragging up increases value and submerges crowns, making top=water semantically); otherwise an exceptionally complete and polished implementation with correct physics, particle splashes, buoyancy arrows, live info panels, and a full Heureka overlay with confetti.