I liked it!
This is different from other defence games, I liked how you animated them when they died. There is just one small glitch you have there, which is, if you"die" you goto the next level. It should be gotoPrevFrame (forgot the code)....but then again it might be my computer lolz.
I think in the begging levels you should make the guys run faster. Or shoot faster. Cause it gets a little boring. I liked how you can upgrade every five lvls but maybe there should be points...well I guess not its fine how it is.
So this was a good game, some few adjust ments it it will be great... Switch the codes for dieing and lvling...I think I test it one more time.
Good luck!