Fun
Falling Sand Game
Pour sand, water, oil, acid and lava into a pixel sandbox and watch them fall, flow, burn, dissolve and react with each other.
Sand: Falls and piles up; sinks through water and oil.
300 × 200 cells. Hold to pour; drag to draw lines. Save keeps one sandbox in this browser.
Play and explore in your browser. No account needed.
Frequently asked questions
What do the materials do?
Sand falls and piles up in slopes and sinks through liquids. Water, oil, acid and lava flow and settle by weight, so oil floats on water. Stone, wood, ice and plant stay where you draw them. Fire rises and dies out, smoke drifts up and fades, and steam rises and condenses back into drops of water.
Which materials react with each other?
Fire ignites wood, oil and plants, and melts ice. Wood burns slowly and gives off smoke, while oil flares up fast. Water puts fire out and turns to steam; water touching lava turns the lava into stone and itself into steam. Lava sets things alight, acid dissolves sand, stone, wood, plants and ice while using itself up, plants grow into water, and ice slowly freezes the water it touches.
How does a falling sand game work?
The sandbox is a grid of 300 × 200 cells, each holding one material. Every frame, the simulator walks the grid from the bottom up and applies simple local rules to each cell: a grain moves down if the cell below is free or holds a lighter liquid, otherwise diagonally; liquids also slide sideways; neighbours can react. This kind of model is called a cellular automaton, and complex-looking behaviour such as sand piles and waterfalls emerges from those few rules.
Is it realistic?
It is a game model rather than a physics simulation. Real sand piles do form slopes at a typical angle of repose and oil really is less dense than water, but here heat is not tracked as a temperature, water freezes only next to ice, and reactions happen with fixed probabilities chosen to look and play well rather than measured rates.
Where is my saved sandbox stored?
In your browser’s local storage on this device, as a compact run-length encoded copy of the grid, usually a few kilobytes to a few dozen. Nothing is uploaded. One save slot is kept; saving again replaces it. Clearing your browser data or using a private window removes it.
Why does it pause when I switch tabs?
The simulation stops while the page is hidden so it does not use battery in the background, and carries on where it left off when you come back. If your device is set to reduce motion, the sandbox starts paused and the fire and lava shimmer is turned off; press Play to start it.
About this tool
This falling sand game is a free sand simulator that runs entirely in your browser, with no download or account. It follows a genre of pixel sandbox toys that grew out of early-2000s web applets and was popularised by games such as Dan-Ball’s Powder Game and, later, Max Bittker’s Sandspiel. You get twelve materials — sand, water, stone, wood, fire, oil, acid, plant, lava, ice, steam and smoke — plus an eraser, and every one of them interacts with the others.
Under the hood the sandbox is a cellular automaton: a grid of 60,000 cells, each storing its material, a small life counter used by fire, smoke and steam, and a colour variation that gives sand and stone their grain. The grid is updated in place from the bottom up, alternating left-to-right and right-to-left each tick so piles do not lean one way, and a per-tick stamp stops any cell moving twice. The result is written straight into canvas image data, which keeps it at 60 updates a second: one update and redraw takes well under a millisecond on a laptop.
Density decides how liquids and grains layer: sand sinks through everything liquid, lava is heavier than acid, acid heavier than water, and oil floats on top of them all. Reactions are local too. A flame touching wood can set that cell burning for a couple of seconds, throwing new flames upward and leaving smoke; water on lava leaves a crust of stone and a puff of steam, which is a fair cartoon of how real lava is quenched.
Some ideas to try: build a stone bowl, fill it with water and pour oil on top, then drop in a spark; stack wood under a lava flow; carve a channel through a stone wall with acid; or grow a plant up through a pool. Pause and Step let you watch a reaction one tick at a time, and Save keeps your favourite scene in this browser for next time.