It's quite cute, but I'm surprised that you're surprised that JS can do it - it's only a few hundred moving objects, and JS has within-order-of-magnitude of native performance.

For shinier stuff, see the demoscene eg https://www.youtube.com/user/Annikras . Demoscene programmers love generative systems, especially when targetting the 4 kilobyte executable category. For example this one, which looks like a distorted Menger sponge: https://www.youtube.com/watch?v=E3qn1RsJlUM