Nice music. Graphics are decent, although the very small scale is not ideal for pixel art (on the other hand, I understand that the small scale helps give the player increased situational awareness). The enemies have a very cool visual design; it would be cool if they also had some music to accompany their appearance.
Also, at one point I seemed to be up against an invisible wall of collision. I think either the obstacle needed to be visible, or it needed to be gone. I took a screenshot, although it's very hard to see:
