This is definitely front page quality work, so pat yourself on the back! I liked the concept, the upgrade system, all of it!
The only issues I saw, was that there would be times when there were absolutely no enimeis on the screen, I had that last for 40 seconds once. I also had a bug show up (this was around wave 7 or 8 that it started I believe, right after I had maxed out my upgrades) where I would shoot a rocket out of the sky, but it would leave a 'ghost' image of the rocket on the screen. It didn't interfere with gamplay at all, it was jsut a little bug.
Congrats again on the great work!