For anyone having trouble in any of the levels: The best advice I can give is to use sniper towers. Make a sniper, make a speed boost, make a 2nd and 3rd sniper. then boost with dmg, and add an aoe slow. Good luck. :)
It's somewhat of a puzzle game, and executed nicely, in my opinion. Just because most of you can't figure it out, that doesn't mean that it sucks. Learn to suck less at games. Sheesh.