Not bad, but too easy and repetitive
First of all, this game is EXTREMELY EASY. Some people are saying that it's really hard becuase they haven't figured out one key aspect of the defense that totally takes down the difficulty level of this game...
With that said, the game becomes quite repetitive on mission mode, since it's the same thing over and over again without any real threat.
Also, there's a bug in that if you have auto regeneration, your health just keeps going up and up. Another issue is that airstrikes are next to useless and some of the reflected shots don't damage enemies.