Excelent, Addictive, and a little sadistic :P
That's all I have to say about this game. It's almost perfect but not quite.
For starters, the collison detection is overly sensitive at the bottom. If you stay at the bottom of the screen, the game thinks that the enemies are being hit constantly, and they die even before getting on the screen. This also works for the bosses, which get killed instantly.
Also, the "thanks for playing" screen loops. Other than these two problems however, it's an almost perfect game. Congrats on a well made game.