✓ 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 (min=0 at top labeled "LUFT", but dragging down increases value toward "WASSER" — actually this is correct labeling but the crown movement goes from top-air to bottom-water correctly; however the slider's native vertical orientation with writing-mode bt-lr means value=0 is at bottom by default, so "LUFT" is visually at top but value=0 maps to crown-in-air which is consistent — but there is no smooth fall animation, only instant position snapping driven by the slider, and the splash fires too early (at progress=0.5, not at water surface contact).
Slider direction is inverted (min=0 at top labeled "LUFT", but dragging down increases value toward "WASSER" — actually this is correct labeling but the crown movement goes from top-air to bottom-water correctly; however the slider's native vertical orientation with writing-mode bt-lr means value=0 is at bottom by default, so "LUFT" is visually at top but value=0 maps to crown-in-air which is consistent — but there is no smooth fall animation, only instant position snapping driven by the slider, and the splash fires too early (at progress=0.5, not at water surface contact).