✓ 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 is inverted (min=0/top=air is correct in intent but the CSS `appearance: slider-vertical` on a standard range likely renders bottom=0/top=100, and the water-level formula collapses to a constant since displacedVol/totalVol = depthFraction regardless of crown, making both containers rise identically; mass/volume/density values are static HTML rather than live JS-driven; fall animation missing — crown jumps linearly with no drop/gravity feel.
Slider is inverted (min=0/top=air is correct in intent but the CSS `appearance: slider-vertical` on a standard range likely renders bottom=0/top=100, and the water-level formula collapses to a constant since displacedVol/totalVol = depthFraction regardless of crown, making both containers rise identically; mass/volume/density values are static HTML rather than live JS-driven; fall animation missing — crown jumps linearly with no drop/gravity feel.