Dude, there's a cheat in this game in the tunnel. You have to hit the bricks close to the end of the tunnel with your weapon. If you did it right, the door won't close when you leave the tunnel. Walk back and grab the floating thing in the tunnel. Your weapon sparkles and you can kill the boss with it. Kind of hard to pull off, but totally worth it!
2/5. This is one of the most boring games I have ever played in my life, which is surprising since it's so fast-paced. There is no challenge, and there is no variety. You shoot the same freaking enemies for what seems an eternity, and the final challenge? Shoot more of them. For ten minutes. Arrgh.