It's even been done with Conway's Life.

https://www.conwaylife.com/wiki/Turing_machine

It's too bad Notch never finished that space-themed game he was once planning. I remember when HN went crazy with implementations of his spec for a simple, memory-mapped 8-bit computer that was going to be central to that game.

I'm planning to introduce scripting into my procedurally generated space game with over 2^100 locations. All entity AIs will be s-expressions, which implement a blackboard architecture. This can readily be mapped to both finite state machines and behavior trees. What's more, a variety of scripting language subsets could compile to the same s-expressions. I want to let players license their scripts to other players for in-game money. Players can also perhaps use "hacking" powers, where they can modify scripts of other entities or ships using regexes. (With the caveat that if they cause a syntax error, they get "feedback damage.") Also, these s-expressions can be subject to genetic algorithms, and will also "breed" in the wild. (As described by Koza in his book Genetic Programming)