This is a real gem. The pixel art, music and gameplay all combine beautifully. This is something I'll probably be playing for a long time. It's really bloody addictive XD. Well done.
The only critique I have (and really, this is the only critique) is that I didn't know how much health I actually had. Maybe making that apparent would make things a little better.
None the less, I love shoot-em-ups which try something different, and this is really great. Well done overall :)