Not bad for an early game, but a little bit more work is needed. The graphics are fairly plain, which I don't mind, but I know other people will. More colours and designs would fix that. Also, the lack of sound and music needs to be fixed (don't forget a mute button). Alternate control schemes would be even better (i.e. WASD or arrow keys). Should be longer too; only 4 levels in and I'm greeted with a "YOU WIN!" screen, which I have to refresh if I want to play again. I'll give it a 3, but I strongly recommend you fix it up a bit if you want people to play and like it.
Level 40 is entitled "Frustration". Let me tell you that it's very aptly named. There are at least 20 exits that are very close but just out of your range, like just a little under lava or a little out of your jump height.
A perfect score on the Pistol Room is worth 53,000 points. In order to get this achievement, you'd have to have 100% accuracy, missing no more than two targets. Good luck!