Not bad!
This isn't bad at all. I had fun, and that's more than a great accomplishment. Most games just aren't my style, this one was actually amusing!
And I agree, it'd look much better (and be more interesting gamewise) if the enemies actually faded in, instead of popping up out of nowhere. Other than that, this was some sweet gaming. You might also want to add a mouse-control option for lazy folks. :P