This game could use a lot of work. The art and animations are pretty stiff, and the pacing is far too quick. I did like the affect of the sprites getting smaller as the went into the background, though.
The music is alright, but a bit forgettable. The character especially is very stiff, and he moves faster than you'd expect based on his animation. On the opposite end of that spectrum are the enemies, which seem to have fast paced animations, but move rather slowly.
If you could upgrade your gun, or at least have an auto-fire, I think the game would be a lot better.
As it stands, it's not all that good of a game, but it can clearly be fixed with a bit of work.
Best of luck.