Star Wars
B2/S345/4 — like Brian’s Brain, but firing cells can hold on
Firing cells can hold their state if enough neighbours are firing, which produces long straight beams alongside the travelling sparks.
How it works
In plain English, before the notation
This is Brian’s Brain with two changes: a firing cell can keep firing if three, four or five of its neighbours are also firing, and there are two recovery states instead of one. The first change is what matters — because activity can sustain itself where it is dense enough, you get long straight beams that persist, alongside the travelling packets.
Beams and packets together
- Open Presets and load "Star Wars Beams", then press Play.
- Look for the difference between the two kinds of structure: short packets that travel, and long lines that stay lit.
- Pause and use the Eraser to cut a beam in half. Both halves usually survive.
Starting configurations
Loads straight into the simulatorTry any rule
The catalogue covers a few dozen rules. Here you can run any of the 262,144 two-state grid rules, or any of the 256 one-dimensional rules, including ones nobody has written up.
Well-known rules
Where it came from
From Mirek Wójtowicz’s MCell collection of Generations rules, where it is one of the standard examples used to show what the survival set does in this family. The name refers to the appearance rather than to any property of the rule.
The rule, precisely
What each cell looks at
The 8 cells touching it, including diagonals (the Moore neighbourhood)
What a cell can be
Four states: 0 = ready, 1 = firing, 2 and 3 = recovering
The update
if state = 0 and (firing neighbours) = 2 then 1; if state = 1 then 1 when firing neighbours in {3,4,5}, else 2; if state = 2 then 3; if state = 3 then 0
B2/S345/4: Birth on 2 firing neighbours, Survival on 3, 4 or 5, and 4 states in total (one ready, one firing, two recovering).
Two kinds of structure at once
Adding a survival condition to a Generations rule changes what can persist:
- Straight beams of firing cells sustain themselves as long as they stay dense enough.
- Travelling packets still exist, as in Brian’s Brain, and coexist with the beams.
- Where a packet meets a beam the result depends on the angle — sometimes the beam survives, sometimes the collision destroys both.
- The longer recovery period leaves a more visible trail, which makes the direction of travel easy to read.
Not established
Beams behave like wires and packets like signals, but nothing has been assembled from them.
Sustained versus transient excitation
Compared with Brian’s Brain, this rule shows what happens when an excitable medium can sustain activity locally instead of always relaxing. Standing structures become possible alongside travelling ones.
Things to try
- Draw a long straight line of Firing cells and press Play. Whether it survives depends on how thick you drew it.
- Compare directly with Brian’s Brain at the same soup density — the difference is entirely down to the survival set.
- Set Cell Scale to 2px for a large grid; the beams need room to be visible.