This is awesome! A few years ago I built a more rudimentary version of a falling sand game with just Javascript and WebGL: http://ericleong.me/sand.js/

I tried to embed the "scripting" language as a texture in WebGL to keep the implementation very fast (note that every pixel is a cell), but I think I worked myself into a corner.

Source code here: https://github.com/ericleong/sand.js