String Rewrite Systems are abstract machines that can only replace parts of a string with another. A rule is made of two statements, where "left" is replaced with "right":
<> left right
The system will attempt to do rewrites until no matches in the input string can be found and the program will terminate.
But most importantly, it's super fun to use to draw graphics.
@neauoire have you played with context free art or a similar rewriting system? Basically a probabilistic extension - rewrites have a chance of happening or not