✓ 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 (label says ▲ Air / ▼ Water but slider default value=0 maps crowns to air and increasing maps to water, which is correct mechanically, yet the vertical slider CSS uses writing-mode+direction:rtl meaning dragging down increases value — this is non-intuitive/inverted UX); no autonomous fall animation (crowns only move when user drags slider, no self-playing fall sequence).
Slider direction is inverted (label says ▲ Air / ▼ Water but slider default value=0 maps crowns to air and increasing maps to water, which is correct mechanically, yet the vertical slider CSS uses writing-mode+direction:rtl meaning dragging down increases value — this is non-intuitive/inverted UX); no autonomous fall animation (crowns only move when user drags slider, no self-playing fall sequence).