I got the key, but I was really disappointed that there wasn't a congratulatory screen or anything like that. Haha!
The game has a good concept and an interesting puzzle idea. Maybe in the next levels, there could be special cubes that only project on certain walls or when they're turned a certain way.
However, please make the smaller character move faster. It's really frustrating to walk the whole level and then realize you misplaced a block, making the jump impossible, for tou to then walk the same way again.