I absolutely love it! Simple but strong mechanics. Even when multiple characters are introduced or exits are moving, you get what you have to do. You did a lot with the animation! Even though the main character and the the rest a just big blocky things, you made them come to life!
But I have to agree with another users comment that this is all about the level design. You only have a handful of sprites in here but it's fun because you found new ways to keep using them.
Oh and the music is just superb. Nice work!