@ apollonianking: I know, it is not really a 5-stars game but it's my firts one, there will be music soon (I hope). Furthermore, it's clearly said in the instructions that you have to shoot the asteroids, but you can shoot the ships too if you have the green missiles... That are power ups !
So your are wrong in this point : there are 3 kinds of power ups (health, shield or powered missiles).
About the graphics and the sound, you are right.
That said, thank you for your comment, I'll try to improve these parameters for the next time.
 "Asteroid"){kind=icon}