For a mouse controlled game, the ship needs to be a lot faster. It lolls around at the turns, which makes the game more difficult not for the skill needed, but because of the poor control you have over the ship. The weapons are fine, but the upgrade system needs work, such as losing all of your work after one hit. It makes the player feel as if the game is just flipping them off, and that you don't care whether anyone plays it or not. Remember that you want your game to be difficult, but enjoyable at the same time.
I give it a C+, or a 5.