Another great space shooter.
My only complaints are: When you have upgraded everything, what else is there to do with the money you've earned? Perhaps if the game had some Extra Lives to spend the money on, then it would be okay. Maybe even a Health Extension icon to spend it on to last longer in battles.
Also, when you lose a life, how about some 4 second or 5 second invincibility?
And a minor one: When you defeat the final boss, there should be a medal for Game Completion.
Other than those, the game is playable and enjoyable.