Fire
Fire is a short-lived, brightly glowing gas that rises, spreads into fuel and then burns out on its own.
- Movement
- Gas — rises, then fades
- Weight
- 1 / 9 (heavier sinks through lighter)
- Lifetime
- Short-lived — fades into empty space
- Glow
- Bright
Fire has weight 1 and moves as a gas: it climbs through empty space, and anything heavier, from sand to water, drops straight through a flame. Each fire cell has a fixed lifetime of 45 ticks, and because the simulation advances once per screen refresh, an isolated flame is gone almost as soon as it appears; on a faster display it burns out sooner.
It survives by spreading. The fire’s table turns touching wood into fire at 15 percent per check, plant at 30 percent and oil at 50 percent, and those fuels have matching entries of their own. Each ignition leaves the original flame burning and adds a new one, so a fire on a large fuel mass looks like a travelling front: freshly lit cells along the edge and empty space behind, where older flames have expired.
Gunpowder is the fastest fuel of all, catching 85 percent of the time it meets a flame, which is why a powder trail burns end to end in a flash.
Several materials put it out. Water turns both itself and the flame into steam at 90 percent. Ice melts on contact at 60 percent, turning the flame into steam and itself into water. Stone, metal, wall, sand, salt and ash have no reaction with fire and are never burned by it; the solids stop a flame from rising, while those powders simply fall straight through it.
Real fire is a chemical reaction that needs oxygen and gives off heat, smoke and ash. Sandlab’s fire behaves more like a contagious glowing particle: it needs no air, transfers no heat beyond its fixed contact rules and leaves nothing behind. Smoke and ash appear only where you paint them.
Try it yourself
- Burnout. Paint a dab of fire in an empty area. It drifts upward a short distance and fades after 45 ticks, leaving nothing at all.
- Fuel ladder. Build a vertical stack with wood at the bottom, plant above it and a layer of gunpowder resting on the plant, then light the wood. The burn creeps through the wood, speeds up in the plant and tears through the gunpowder.
- Water curtain. Keep a steady stream of water falling between a fire and a wooden wall. Flames that drift into the stream turn into steam, and the wall survives for as long as the stream keeps running.
Reactions
Odds are per contact check: each tick, touching cells inside the same two-by-two block are checked against the reaction table, so even a small chance happens soon after contact.
When fire touches something
- Touching Wood: turns the Wood into Fire. (steady, 15% per contact check) →
- Touching Oil: turns the Oil into Fire. (fast, 50% per contact check) →
- Touching Plant: turns the Plant into Fire. (fast, 30% per contact check) →
When something touches fire
- Touching Wood: the Wood turns into Fire. (steady, 12% per contact check) →
- Touching Plant: the Plant turns into Fire. (fast, 35% per contact check) →
- Touching Ice: the Ice turns into Water, and this Fire turns into Steam. (fast, 60% per contact check) →
- Touching Gunpowder: the Gunpowder turns into Fire. (almost instant, 85% per contact check) →
- Touching Water: the Water turns into Steam, and this Fire turns into Steam. (almost instant, 90% per contact check) →
- Touching Oil: the Oil turns into Fire. (fast, 50% per contact check) →
Tip
To contain a blaze, take the fuel out of its path or put water in front of it. Flames only move upward on their own, so fuel stored below or beside a fire is in less danger than fuel above it.