Boring??
Boring? Yes, might be a bit boring... But it should be used whilst playing another game. When you get time, go back to this game and build stuff and go on with the level. Then, whilst this game is defending, you can kill zombies, pacmen, homosexuals or Jesus'... I find it quite amusing, good way to kill time.
Overall? 7/10
P.s make another game like this! I'd recommend it...