✓ 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 starts crowns at top/air, increasing value moves them down into water, which is correct), but the writing-mode/appearance approach for vertical orientation is non-standard and unreliable cross-browser; additionally the water-rise scale factor is cosmetically minimal and the splash triggers are tied to narrow percent ranges making them easy to miss.
Slider direction is inverted (value=0 starts crowns at top/air, increasing value moves them down into water, which is correct), but the writing-mode/appearance approach for vertical orientation is non-standard and unreliable cross-browser; additionally the water-rise scale factor is cosmetically minimal and the splash triggers are tied to narrow percent ranges making them easy to miss.