nice but simple
Well- Good graphics and decent music. The gameplay was very repetitive, with lvl 11 essentially the same as lvl 1-10. Since all the enemies behaved roughly the same, there wasn't any challange other then figuring out WHAT just damaged you. Because neither could I see nor hear an enem ship firing at me, nor did it crash into me - still I got damaged sometimes.
Add more bosses and some changes to the enemies (breaking up asteroids, missile firing ones etc.) and perhaps get some more choices of weaponry into it.
For the upgradeshop - please include a display of the current shipstatus.