Hi there! I appreciate the efforts you put in the game.
My suggestions:
1. Add sound effect(s), even a simple one would make the game better ;)
2. The control feels i little bit weird. Maybe you should seperate shooting from movement. I mean, use the mouse for aiming and shooting, and use arrow keys to move (just my suggestion)
And..., I can actually just stand still in the corner, waiting for the enemies to come and then kill'em all
Lastly, Congratulations for finishing your first game! Keep in mind that almost everyone's first game would not be a huge, shiny game. And I know that starting is easy, but it's difficult to finish making a game. So once again, congratulations! And don't stop ;)