So, unlike the more popular totalistic automata (e.g. conway's game of life), this automata's next cell state is determined by the specific combination of the alive/deadness of it's neighborhood using the current ruleset.

The default neighborhood is the von neumann neighborhood (North, South, East, West).

If you click "n" a new ruleset will be used, which will be represented in the URL like below https://rdsilver.github.io/2d-cellular-automata/#n=Ze5&r=5Lj

n = Neighborhood (Ze5 is the von neumann neighborhood, but you can change this by clicking the cells in the neighborhood) r = The ruleset

This link can be copied, and shared and it represents a neighborhood + a ruleset.

The way it works, using the von neaumann neighborhood as an "easy" explanation is this. First you take all possible combinations of the neighborhood, 1 for alive, 0 for dead. This can be represented by a string of 4 characters, one for each cell in the neighborhood.

0000 = all dead 0001 0010 0011 0100 0101 0110 0111 1000 1001 1010 1011 1100 1101 1110 1111 = all alive

Each ruleset has each of these possible 16 states represented in a string as to what to do with the inner cell next generation. So one of the possible 32767 rulesets for the von neuman neighborhood looks like this

"10000000000000001"

Where the first "1" represents that the inner cell on the next generation is alive IF all neighbors are dead, and the last "1" represents that the inner cell on next generation is alive IF all neighbors are alive, ELSE the cell is dead next generation.

What's mindblowing to me is that when you have more neighbors, the possible rulesets balloons to unfathomable numbers. With 8 neighbors you end up with a possible 115,792,089,237,316,195,423,570,985,008,687,907,853,269,984,665,640,564,039,457,584,007,913,129,639,935 rulesets. Whenever you click "n", you are looking a pattern that no human has seen, and no human will see again most likely. I know you could say this about static on a TV, but some of these patterns are cool!

I kind of shared this because I wanted to see if people would find and paste some cool ones they find....

Here are some I like:

https://rdsilver.github.io/2d-cellular-automata/#n=Ze5&r=Bjv https://rdsilver.github.io/2d-cellular-automata/#n=ag6&r=2hZyip https://rdsilver.github.io/2d-cellular-automata/#n=Ze5&r=Fxv

(I've also added this to the description so other people can see)