Pixel physics sandbox

Falling Sand Simulator

Paint with sand, water, fire, lava, oil, acid, ice, plants and gunpowder, and watch them interact. Sand piles up, oil floats on water, fire spreads through wood, lava turns water into steam and stone, and gunpowder fuses burn to a big blast.

PAINTINGSand
BRUSH4
PIXELS0

Draw with the left mouse button or a finger. Erase with the right button or by holding Shift. Keys: 1–9 pick a material, [ ] brush size, Space pause, Ctrl+Z undo.

How the simulation works
  1. The canvas is a grid of pixels and each pixel holds one material. Every frame, each pixel looks at its neighbours and follows simple rules.
  2. Powders (sand, salt, gunpowder) fall and slide sideways into piles. Liquids flow sideways and settle by density: oil floats on water, sand sinks through both. Gases (smoke, steam) rise and fade.
  3. Reactions: fire spreads to wood, plants, oil and gunpowder; water puts out fire and turns to steam; lava turns water into stone and steam; acid dissolves most things (not metal); ice freezes water and melts near heat or salt; plants grow into water.

This is a playful model of physics and chemistry, not an exact simulation. Everything runs in your browser.

Using Falling Sand Simulator

A pixel physics sandbox. Paint with sand, water, stone, wood, fire, lava, oil, acid, plants, ice, salt and gunpowder and watch them fall, flow, burn and react with each other.

  1. Pick a material in the Materials tab (or press 1–9) and draw on the canvas. Hold the button to keep pouring.
  2. Erase with the right mouse button or by holding Shift. Change the brush size with the slider or [ and ].
  3. Load a scene such as Hourglass, Volcano, Forest fire, Density layers, Acid lab or Gunpowder fuse.
  4. Add wind in Settings, choose a higher resolution, or save your world as a scene file and load it later.
  5. Undo mistakes with Ctrl+Z and download a PNG snapshot of your creation.

Example

Density layers: sand sinks through oil and water while oil floats on top — materials sort themselves by density.
Gunpowder fuse: light the end of the line with fire; it burns along and the pile explodes.

Questions & answers

What is a falling sand game?

A sandbox where every pixel is a material that follows simple rules: powders fall and pile, liquids flow, gases rise and some materials react. Complex behaviour emerges from these small rules.

Which reactions are there?

Fire burns wood, plants, oil and gunpowder; water puts out fire and becomes steam; lava turns water into stone and steam and ignites things; acid dissolves most materials except metal; ice freezes water and melts near heat or salt; plants grow into water; steam can condense back into water.

Why does oil float on water?

Each liquid has a density. Denser materials sink through lighter liquids, so sand sinks through water, and water sinks below oil.

How do I make a fuse?

Draw a thin line of gunpowder to a big pile and touch the end with fire. A thin line burns along; a thick pile explodes.

Can I save my world?

Yes. Save scene downloads a small JSON file; Load scene opens it again. Nothing is uploaded.

It runs slowly. What can I do?

Choose a smaller resolution in Settings, lower the speed, or turn off the glow in View.

Is it a real physics simulation?

It is a playful cellular automaton inspired by real physics and chemistry, not an exact simulation.

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