✓ 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 → crowns in air is correct, but HTML range default renders bottom=0 for vertical, so dragging down raises the value and submerges crowns — visually bottom=air, top=water); mass/volume/density displays are static not live; no fall animation (crown teleports linearly); water rise is cosmetically proportional but not physically scaled to displaced volume difference between the two tanks.
Slider direction is inverted (value=0 → crowns in air is correct, but HTML range default renders bottom=0 for vertical, so dragging down raises the value and submerges crowns — visually bottom=air, top=water); mass/volume/density displays are static not live; no fall animation (crown teleports linearly); water rise is cosmetically proportional but not physically scaled to displaced volume difference between the two tanks.