[hopfog]

Actually even higher level than that: it's all JavaScript, but it relies heavily on multithreading (see the linked Noita talk, which uses the same model). But basically:

The world is divided into chunks and the threads are processing them simultaneously in an even-odd checker pattern to avoid race conditions. When all pixels settle in a chunk it falls asleep and can be skipped altogether until an active pixel enters and wakes it up again.