SandLab

SandLab is a falling-sand physics sandbox with over 270 materials that react to each other without any extra input from you: pour lava into water and watch it hiss into steam and harden into stone, let acid eat through metal, or watch current run along wires and plants grow toward water. Room settings let you push temperature from deep-space cold to blazing heat, flip or kill gravity, and add wind, with one-click presets like Moon, Arctic or Inferno if you want a themed starting point.

Short goals — boil water, grow a plant, make glass, forge bronze — point toward new experiments without forcing a particular order, and a lab notebook tracks how many of the 199 possible reactions you've actually discovered.