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

Other things you ought to take a look at:

Sauerbraten in JS, called Bananabread¹, and jor1k an OpenRISC emulator running Linux². Although the latter uses a relay for networking.

1: https://developer.cdn.mozilla.net/media/uploads/demos/a/z/az...

2: https://s-macke.github.io/jor1k/demos/main.html