This is fun to see on HN, which has shown a (justifiable) affection for L-systems.
I wonder if an example that is closer to the original root of L-systems (biological/botanical shapes, like trees) would be a nice addition the the initial basic examples?
Just a detail on styling. The white text/ black background combination is kind of hard on the eye since it's too much contrast. I would use a lighter shade of black for the background. Something like #0f0f0f would work.