I agree with 90% of what catinbootsMI said.
While the addition of WASD controls is definitely a good idea, please do not strip the game of arrow controls. Many programmers who are not left handed do not realize that lefties often prefer the arrows, if they are using the mouse with their left hand. Both control methods are used, so I would advise you test yourself and figure out how to make both accessible to the game.
Also, you may want to randomize the shooting pattern of your enemy a little more. I left the game running while writing this and didn't get hit a single time.
Looking forward to your future submissions.