Guide
How to Play the Falling Sand Game
The falling sand game is a physics sandbox with no goal. Pick a material, paint it onto the grid, and watch powders fall, liquids flow, gases rise, and reactions play out.
Play the Falling Sand GameThe basics
Paint a material and let physics run
The falling sand game is a grid of cells. Every frame, the whole grid is simulated: each cell of sand tries to fall, each cell of water tries to spread, each cell of fire tries to rise and to ignite what it touches. You never move cells directly — you drop material in with a brush and the rules do the rest.
There is no score, no timer, and no way to lose. Some people build elaborate machines; others just flood the screen with lava. Both are playing it right.
Open the sandbox whenever you want to experiment; use this guide for the controls and the physics behind each material.
Controls
Mouse, touch, or keyboard
Every method paints the same cells. Pick whichever suits the device in your hand.
Everywhere
Click / touch and drag
Hold the pointer down and move it to paint a continuous stroke of the selected material. The stroke is filled in between pointer samples, so fast drags do not leave gaps.
HUD + [ ]
Brush size
The size control sets the brush radius in cells. On desktop the [ and ] keys step it down and up. A small brush is good for fuses and seeds; a large one for terrain and floods.
Desktop
Keyboard
Space pauses and resumes the simulation, C clears the canvas, M mutes sound, and the number and letter keys jump straight to a material (1 sand, 2 water, and so on). Every on-screen control also has a visible focus ring.
The loop
Four steps you repeat forever
- 1
Pick a material
The palette on the right holds every material: powders like sand and salt, liquids like water, oil, acid, and lava, gases like fire, smoke, and steam, plus wall and plant. Tap one to load it into the brush. The eraser is the first swatch.
- 2
Paint onto the grid
Press and drag anywhere on the canvas to drop material under a round brush. Powders start falling immediately, liquids spread out, gases rise. Use the brush-size control to go from a fine trickle to a wide pour.
- 3
Watch it react
Every frame the whole grid is simulated. Materials fall, flow, and collide, and neighbours react: fire spreads along oil, lava sets stone in water, acid eats through solids, plant creeps into a puddle. Nothing is scripted.
- 4
Pause, clear, repeat
Pause to freeze a moment or place material precisely, then resume. Clear wipes the canvas back to empty air so you can start a new scene instantly — there is no reload and no round to lose.
The physics
Four families, one rulebook
Every material belongs to one of four families, and its family decides how it moves. Reactions between materials are covered on the elements page.
Powders
Sand, salt, and stone fall straight down until blocked, then tumble to the side to form a slope. Stone is heavy gravel and barely slides, so it stacks in steep columns; sand and salt spread into gentle hills. Powders are denser than liquids and sink through them.
Liquids
Water, oil, acid, and lava fall, then flow sideways to level out. Density decides what floats: oil rises above water, water sits above nothing, lava is the heaviest. A lighter liquid poured under a heavier one bubbles up through it.
Gases
Fire, smoke, steam, and gas rise and wander sideways to fill space. Fire and smoke fade after a short life; steam cools and condenses back into water; gas lingers until a flame reaches it and the whole cloud ignites at once.
Solids
Wall never moves or reacts and is the only thing acid cannot dissolve. Wood and plant hold their place but burn. Plant is also alive — it grows new plant into any water it can touch.
Common mistakes
Why a build falls apart
Storing acid without wall
Acid dissolves sand, stone, wood, and plant, so a basin made of anything but wall will spring a leak. Line every acid container with wall on all sides.
Expecting lava to flow forever
Lava hardens into stone the instant it touches water and cools over its lifetime. If you want a long lava river, keep it away from any water and feed it from a steady source.
Painting gas near an open flame
Gas is inert until fire reaches it, then the entire connected cloud flashes at once. If you are filling a space with gas, put out nearby flames first.
Forgetting the pause key
Precise builds — a fuse one cell wide, a seed in exactly the right spot — are far easier with the simulation paused. Place, then press Space to let it run.
Things to try
Starting points, not instructions
- Build a stone basin, fill it with lava, then drip water on top to grow a solid island one cell at a time.
- Float a layer of oil on a pool of water, cap it with wall, and touch one spark to the surface.
- Drop a single plant cell beside a puddle and watch it vine its way up toward the light.
- Line a funnel with wall, pour acid in the top, and aim the stream at a sand wall below.
- Fill a sealed room with gas, leave one gap, and set a flame at the opening.
- Pour sand through a tall column of water to see it punch straight down and build a bar on the floor.
- Make rain: trap steam under a wall ceiling and wait for it to condense and fall.
Where you can play
Same sandbox on phone and desktop
fallingsandgame.app runs in any modern browser with no app to install. Settings stay on the device you played on.
Desktop browsers
Chrome, Edge, Firefox, and Safari all run the simulation with no plugin. Paint with the mouse, resize the brush with [ and ], and use the keyboard shortcuts for pause, clear, mute, and material selection.
Phones and tablets
The layout is touch-first. The canvas and the full material palette sit on one screen in portrait, so you can paint with one thumb and switch materials with the other. Clearing is instant.
Settings on this device
Your last material, brush size, and sound preference are saved in local browser storage, along with lifetime counters like particles placed and materials tried. Nothing is uploaded and there is no account.
Curious what each material does? See the elements & reactions reference or read the FAQ.
Play the Falling Sand Game free