It's a bit similar, but uses GPU and spawns millions of particles. On the other hand, it's less of a sandbox and more of a demo. You can write your own code in the browser too, but it's a bit tricky to program, because it compiles to shader language and it has some weird limitations.
http://tinlizzie.org/~ohshima/shadama2/live2017/
http://tinlizzie.org/~ohshima/shadama2/
It's a bit similar, but uses GPU and spawns millions of particles. On the other hand, it's less of a sandbox and more of a demo. You can write your own code in the browser too, but it's a bit tricky to program, because it compiles to shader language and it has some weird limitations.