Well..
Well, I did enjoy the experience. Some of the levels felt a bit tedious (trial and error and such things), but when the game was over I was left wanting more. I like the grayscale graphics, though they could be sharpened a bit it wasn't a big point. I didn't especially care for the music, but was happily able to shut it off. Some things you may want to think about that could improve the game (in no particular order).
1. As I said before sharpening the graphics couldn't hurt.
2. Adding some good sound effects also couldn't hurt.
3. More levels, always more levels.
4. Time me! Add a level clock, even if you aren't comparing your score to the world it can be nice to challenge yourself. On that note, with the timer you could add a challenge time to beat.
5. Even though the game is pretty simply a breif intro with instructions (or a tutorial level) wouldn't hurt either. It does just kind of throw you into the game.
Anyhow great game, excelent work, keep up the good work.