Here's a pretty minimal implementation of Conway's Game of Life for PICO-8. It has a basic performance optimization (it only updates the active area of the grid), and you can see the active area adjust by setting dbg=true at the top of the code.
That said, it gets pretty slow pretty quickly for larger simulations.
You set up the grid as follows:
Arrow keys -- move the cursor around.
Z key -- toggle a given cell to active/inactive.
X key -- start / stop the simulation.
If you're unfamiliar with the Game of Life, google it :-).
An easy starting point for a cool pattern is a ten cell contiguous row (10 connected horizontal cells).
There are better PICO-8 Game of Life carts, but I had a lot of fun making this.