Okay, here is one before the weekend.
Conway's Game of Life. It is a simple concept. Set up some cool patterns and let it run on a good cycle. I just did it, using '*' and ' ' but feel free to do it graphically if you prefer. Here are the rules, and my code is in the same repo so let that be a spoiler warning:
https://git.qoto.org/Absinthe/life-conway/blob/master/README.md
@billstclair It's supposed to be fun. There are different ones with slightly different rules you might could adapt. But whatever you like. Nice js implementation though