Source: https://github.com/zsoltk/GameOfLife
You can use the codebase to implement your own cellular automata, as it was intentionally designed to be easy: implement your own rules (maybe color mapping for custom states) and you're good to go.
Even if you're not familiar with cellular automata, both playing with the app and discovering the solutions behind it can be fun.
You can also edit the rules in the app to have some pretty interesting results instantly:
