Great source of inspiration :P
I think this is a perfect example of what Mark meant with "don't take mechanic too literally".
The concept is intriguing and its implications are presented well throughout the levels. It makes for engaging puzzles even with only 3 buttons; I can only imagine how far you can take this with more levels and additional classic platformer mechanics or abilities on different buttons. The idea is simple but extensible and has the potential to become very deep, I think.
Certainly one of the best designs!