For a first game, it shows amazing potential!
For your first game this is really good. There were only about three flaws I found with the game. One was, it was a sniper rifle, yet it could be fired rather fast, to me (I'm no gun expert) it seemed a little too fast. That also made the game a little easy. Also, the game was just the same thing over and over again, could use more originality. The final thing was the graphics looked nice, but could be improved, and that will come with time.
All in all great job! 3/5