Grainfall

about/

Grainfall is a falling sand toy. Pick a material, drag across the screen, and watch it react with whatever is already there. Sand piles up and slides back down. Dig a hole and water will find it. Oil floats on top of water, and oil burns. Plants drink from standing water and creep toward it. Fire spreads, leaves ash behind, and boils water into steam that drifts up, cools off, and comes back down as rain.

There is no score and nothing to unlock by playing. What you get is twelve materials that all react to each other, and the fun is working out how. Build a glass tank and fill it with acid, since glass is the one thing acid cannot chew through. Pour lava into water and it sets into stone. Light one end of a gunpowder trail and follow it along.

Hit record at any point and Grainfall turns what happened into a video, with sound built from the same events you just watched. Save a world and it keeps a picture of itself in your list. Send one to a friend as a small file and it opens straight into their copy.

The simulation is a hand-written cellular automaton running at 60 frames per second. Everything else in the app is made the same way: the sounds are synthesized from maths rather than recorded, and so is the icon. No account, no ads, nothing collected, and it all works in airplane mode.