✓ 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 (slider top = value 0 = crowns in air is correct conceptually, but the vertical range input with writing-mode bt-lr maps value=0 to the bottom, so dragging up increases value, meaning top=water/submerged — direction is backwards); ASCII-art rendering is functional but coarse with no true fall animation (crowns teleport rather than animate).
Slider direction is inverted (slider top = value 0 = crowns in air is correct conceptually, but the vertical range input with writing-mode bt-lr maps value=0 to the bottom, so dragging up increases value, meaning top=water/submerged — direction is backwards); ASCII-art rendering is functional but coarse with no true fall animation (crowns teleport rather than animate).