✓ 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 means crowns start in air correctly, but HTML vertical slider with `writing-mode: bt-lr` renders visually upside-down so dragging up increases depth rather than down); mass/volume/density panel values are hardcoded static text rather than live-updating elements, and crowns lack distinct visual differentiation (both use identical goldGradient with no alloy indicator).
Slider direction is inverted (value=0 at top means crowns start in air correctly, but HTML vertical slider with `writing-mode: bt-lr` renders visually upside-down so dragging up increases depth rather than down); mass/volume/density panel values are hardcoded static text rather than live-updating elements, and crowns lack distinct visual differentiation (both use identical goldGradient with no alloy indicator).