Cool Game
Nicely done. I like the implementation of this better than that one slide-puzzle game that won IGF a couple years back. (and I've been craving more of this since Skyward Sword). The black and white graphics work well. The constantly changing backgrounds were a little distracting, and I don't know that there was really any purpose behind them.
Note, it's possible to get permanently stuck. I jumped up and shifted into the h-shaped block before I got that "ceiling key" (the last key you can get that opens the heart room). The h-shaped room should have platforms so you can jump back up. (unless you want people to get permanently stuck, in which case you should make something out of the fact that they've lost at that point)