✓ 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 ▲Air top / ▼Water bottom but the `writing-mode: vertical-lr; direction: rtl` mapping means dragging down increases value toward water, which is correct semantically, yet the vertical CSS orientation flips visually on many browsers making top=100/water and bottom=0/air — a known cross-browser bug with vertical range inputs); otherwise a richly complete ASCII-art demo with correct physics values (Au 19.3, Ag 10.5 g/cm³), live readouts, animated splash, rising water, and a multi-frame Heureka overlay.
Slider direction is inverted (label says ▲Air top / ▼Water bottom but the `writing-mode: vertical-lr; direction: rtl` mapping means dragging down increases value toward water, which is correct semantically, yet the vertical CSS orientation flips visually on many browsers making top=100/water and bottom=0/air — a known cross-browser bug with vertical range inputs); otherwise a richly complete ASCII-art demo with correct physics values (Au 19.3, Ag 10.5 g/cm³), live readouts, animated splash, rising water, and a multi-frame Heureka overlay.