✓ 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 keeps crowns in air, but dragging down — increasing value — lowers crowns, which is correct directionally yet the `writing-mode: bt-lr` + `-webkit-appearance: slider-vertical` means visually the thumb starts at the bottom for value=0, making the perceived direction wrong); submersion fraction calculation is ad-hoc and the water body geometry update mixes pixel units with ml in an inconsistent way, causing the water-level rise to be negligibly small visually, but core physics values (densities 19.3 vs 10.0, same 1000g mass, larger volume for gilded crown) are correct.
Slider direction is inverted (value=0 at top keeps crowns in air, but dragging down — increasing value — lowers crowns, which is correct directionally yet the `writing-mode: bt-lr` + `-webkit-appearance: slider-vertical` means visually the thumb starts at the bottom for value=0, making the perceived direction wrong); submersion fraction calculation is ad-hoc and the water body geometry update mixes pixel units with ml in an inconsistent way, causing the water-level rise to be negligibly small visually, but core physics values (densities 19.3 vs 10.0, same 1000g mass, larger volume for gilded crown) are correct.