Lovely
This is quite wonderful - like others have said, despite the warning in the submission it's at a good level of challenging that rewards you for working out how to bend the rules and how to get past the obstacles, just as they become frustrating. I was surprised that it was over so quickly, but its short length means that it doesn't become a drag.
The music is wonderful, and really, I had to give it a 10 just for that ending - that was a clever moment, and something that made me realize that the game's sort of defiance of your expectations extended even to the graphics and music at that moment.