Not really a game, but what I got done during the Compo. Reaction Diffusion is a cool technique related to cellular automata (like Game of Life). It can result in beautiful, organic patterns. Code is ported from Daniel Shiffman's example in P5 (https://github.com/CodingTrain/Rainbow-Code/blob/master/CodingChallenges/CC13ReactionDiffusion_p5.js/sketch.js) into Pico-8.

WARNING: it runs very slowly, 2-3 seconds per frame on my laptop. I may optimize some more, but I suspect it would be the same on a real old-school 8-bit computer, so that's part of the fun. Leave it running for an hour or so and check back, just like back in the 80's.

You can tweak the feed speed (FEED) and kill ratio (K) to get radically different patterns.