✓ 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 (value=0 at top maps to crowns in air, which is correct semantically, but the label says top=air/bottom=water yet the slider uses writing-mode:vertical-lr with direction:rtl, making the physical drag direction ambiguous/inverted in most browsers); no discrete fall animation — crowns simply translate linearly without a drop/fall event.
Slider direction is inverted (value=0 at top maps to crowns in air, which is correct semantically, but the label says top=air/bottom=water yet the slider uses writing-mode:vertical-lr with direction:rtl, making the physical drag direction ambiguous/inverted in most browsers); no discrete fall animation — crowns simply translate linearly without a drop/fall event.