Really good platformer! The generous checkpoints were appreciated. The ending sequence was pretty difficult but satisfying to complete.
The relationship between the on/off states of the two terrain types was a little confusing. They each have their own button to toggle them independently, but sometimes toggling one automatically toggles the other (but not always?). Not sure if that was intentional. It wasn't very intuitive and made some parts more annoying than I would have liked.
Still, great job overall.