Great entry, would love to see more. I think you forgot to remove the unchangeable rule in the last level. That would be a good idea to take this. Some rules can't be changed, some can only change a little, or you have a limited number of changes, maybe you could collect changes or unlock rules in the level. Endless possibilities really.
(And small tipp, you don't need a quit button in the web version. It just freezes the game until you reload)