Addicting madness
it's all automatic, quite simple and non-attentive after level 15, then through 50 or so then you start getting worried, at 60 you start losing all your units due to the massive amount of waves coming at you, high speeds, more health on the common airplane, eventually all I was left with was my tower that had 20,000 health..made it to level 92 colonel rank is the highest you can get.