✓ 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
All prompt requirements are met with correct physics (gold 19.3 g/cm³, brass 7.8 g/cm³, same 1000 g mass), visually distinct crown sizes, rising water level, splash particles, live readouts, and a polished Heureka overlay — minor weakness is that the slider has no discrete "crowns in air" dead zone so the transition to water contact feels abrupt at the top of the range, and the visual water-rise scaling (VISUAL_SCALE amplifier) is somewhat arbitrary rather than physically derived.
All prompt requirements are met with correct physics (gold 19.3 g/cm³, brass 7.8 g/cm³, same 1000 g mass), visually distinct crown sizes, rising water level, splash particles, live readouts, and a polished Heureka overlay — minor weakness is that the slider has no discrete "crowns in air" dead zone so the transition to water contact feels abrupt at the top of the range, and the visual water-rise scaling (VISUAL_SCALE amplifier) is somewhat arbitrary rather than physically derived.