Not bad.
For being made four years ago.
The characters were very dark, but were easy to kill. The crosshair was a tiny bit to big. I also think you should have unlimited bullets, that way it's easier to brake someone else's high score.
The good thing was, the graphics. You obviously drew the from the actual weapons, enemies and backgrounds, so that was good work. Good intro meny too, even though there only was a go button.
~ Frost