Here are some tips.(if you need them)

First is the animation as you can see,that you still have plenty of work to do and next is the controls,the movement keys work quite well(good work on that) except for the one that shoots,just add a tutorial or write the controls down in the author's comments and thirdly,the concept can be extended with more weapons,upgrades and waves of different enemies and lastly,throw in realistic sound effects and a music track (mute option included) and you should have a real game.

Good game

Would love to see something longer. Good luck

Well...

The art was pretty well done. I also didn't notice many glitches or bugs at all. My biggest complaint is the unoriginality, but if this is your very first flash game, it is understandable that you would want to try out something familiar. In fact, my very first flash game was a very poorly drawn maze game. :p My other, smaller complaint is that there wasn't (as far as I know) a way to lose the game. Lastly, the game wasn't very long. There was only one level.
I commend your efforts since this is a first flash game. I think you have potential, especially in your artwork. Good job! :)