Nice
I can tell you put a lot of work into this. Good job. My only complaint was the poor programming. There's no reason that should have lagged. Get on IRC at freenode in the #gpwiki channel and I'll show you how to fix things. I like that you could turn off the effects though. That helped the against the lag a bit.
Nice structure for the game. However, in the tutorial you should have shows the prereqs to each building and unit. At around wave 9 I lost fairly quick. Why can't you repair your main base. There were times when I had money rolling in an 15 medium tanks, but it still wasn't enough. Tough game I guess. Too bad there are no save points. :( That would have made the replayability a bit higher. I mean the waves are very long.
Also why do you have them attacking from two sides? That is just frustrating to micro manage units with unintuitive control back and forth across the map.
This needs some work. Good luck on your next programs.