Pretty good game. You could have easily created a masterpiece if you just put in a little more effort, but other than that it was an enjoyable game.
Keep in mind the system that you're making this game for. Computers have mice, so take advantage of it. It's sort of difficult to play a game using specifically the keyboard, and mice gives the player a lot more control anyway. It's not a huge issue, but if you added mouse support this would easily be a much better game.
One of the major disappointments in this game was the lack of player development. Your player stays the same the whole game, which is sad because you left a whole bunch of room for upgrades. If you had a shop that sold better weapons or gave you more health in between levels, you'd be set.
Other than those two complaints, this was a really smooth and pretty game. The music was great, and the game play was pretty good. Overall, a good game that's definitely worth playing.