It seems I'm always on the lookout for new windowmanagers. Last year started using Ion3, which I really like. Yesterday I saw a windowmanager called dwm and it is written in about 2000 lines of C code. This is not useful in itself, but it makes it easier to understand the code and make some small modifications without actually understanding all of it. And 2000 lines isn't that much either.
Configuration of dwm is done through editing the source code of the program. Which is actually quite a simple way to make changes.