Nice game!
I think it would be great if you make a sequal with some AI turrets that you could build, so eventually you could have them do some of the dirty work, or maybe you could be able to build a plane or something that would follow a path around the screen and bomb things, or some infantry that could run around that you would have to protect from being run over. I dunno, but I think basically it would be nice if you added some computerized helpers of some sort. Other than the "no backup" lol it was a great game.
My glitch: I had all upgrades and had built everything. On the level with the red tank or whatever, I used a bomb on the first thing to enter the screen to see what it did, but I had also laid 3 mines. At this point, all vehicles did no damage and went right through my base along with their bullets. At first I couldn't hurt them either, but then I used a shock wave thing and it killed all of them (except a tank that got away before I did this) and after that I could shoot them and they couldn't shoot me. It kept up like this and I couldnt hover over the ?s at the bottom of the screen to check my stats. Eventually the badguys stopped coming and nothing happened, so I closed it. I don't have flash player 8, or whatever the newer one is. Hope this helps. Happy bug hunting.