✓ 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 at top means crowns in air is correct visually, but the CSS `writing-mode: bt-lr` / `appearance: slider-vertical` means the physical top of the slider corresponds to max, not min — effectively the thumb starts at bottom=0/air, which is inverted from the requirement); ASCII-art rendering is functional but both crowns share identical Y positions and the crown drawing logic produces garbled output for emoji symbols, weakening the visual differentiation.
Slider direction is inverted (value=0 at top means crowns in air is correct visually, but the CSS `writing-mode: bt-lr` / `appearance: slider-vertical` means the physical top of the slider corresponds to max, not min — effectively the thumb starts at bottom=0/air, which is inverted from the requirement); ASCII-art rendering is functional but both crowns share identical Y positions and the crown drawing logic produces garbled output for emoji symbols, weakening the visual differentiation.