Great job on your first game! I didn't really know what the goal was, I would include some kind of tutorial. Should I just avoid the bullets? Should I try to approach the enemy? Remember that other people aren't you, and they don't know all the secrets of the game like you do.
Also, rather don't make installers for your games. It was statistically proven that games with an installer got worse ratings than games with just the executable for the game.