✓ 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 "push up for depth" but HTML range sliders render bottom=max, so sliding up increases value, which moves crowns down into water — partially salvaged by browser behavior but the UX label is confusing), and crowns jump abruptly into water at depth>40% with no smooth fall animation; mass/volume values in the data panel are static rather than dynamically updating with submersion fraction.
Slider direction is inverted (label says "push up for depth" but HTML range sliders render bottom=max, so sliding up increases value, which moves crowns down into water — partially salvaged by browser behavior but the UX label is confusing), and crowns jump abruptly into water at depth>40% with no smooth fall animation; mass/volume values in the data panel are static rather than dynamically updating with submersion fraction.