... well, to begin with, let me just say that this game just oozes quality, from start to finish! But, since I have exactly 4 critisims to make of the game, I'll start with them:
First off, the enemies types could have been slightly more varied, I only counted 5-6 diferent enemies, so a little more variation would have been nice (specailly the bosses); the fact that the ship changes the direction it faces when it turns was, in my opinion, a bad gameplay decision, it makes aiming the shots too dificult and creates frustation; given the previous problem, the ratio powerup drops could have been slightly higher to compensante this, especially "shot" powerups; finally, there was a slight bug in the bonus levels that allowed me to transerve through the obstacles (i.e., hit detection problems). But that's it. The rest, as you will see, was pretty much perfect.
And to begin with, the coordination between the music and the gameplay was absolutly spot-on perfect, which I imagine is really hard to do, and the choice of music was interesting and well picked. The graphics were great, simple but "clean" and (again), went well with the game. The gameplay, albite not very "new", was well executed and actually had a few original elements and the controls were pretty good (although the mouse was a bit "floaty"). I really liked the idea of the bonus levels too.
All in all, this is a really good game, so big kudos and cheers!