Neat concept. However, I feel like the levels are too big and involve way too much walking. A puzzle shouldn't just be difficult because of it's size. Furthermore I would have liked some intermediate door to guide the player through the level. The average short term memory can only fit 7 things, so for the last level I found myself mostly wrestling with my own incapability instead of the level. ;) The idea has definite potential though, could imagine it mixes well with the ideas of this game as well.