✓ 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 (thumb at top = air is correct conceptually but the drag maps y=0→top to sliderValue=0 which means crowns START above tank — actually direction may be correct — however the slider thumb starts at top (value=0, crowns in air) and moves down to submerge, which is correct, but the custom drag-slider lacks accessibility and both crowns share the same X position/emoji making them visually overlap in the single tank.
Slider direction is inverted (thumb at top = air is correct conceptually but the drag maps y=0→top to sliderValue=0 which means crowns START above tank — actually direction may be correct — however the slider thumb starts at top (value=0, crowns in air) and moves down to submerge, which is correct, but the custom drag-slider lacks accessibility and both crowns share the same X position/emoji making them visually overlap in the single tank.