Great game!!
This is one of the best turret games in a looong time. I love it. And for the people who have difficulties with beating the ninja boss in lvl 14. Try building just undead/ico towers in the top left part. If you upgrade them to the mana leach version they gain a disarm bonus which renders je smokebomb useless. This way you got a chance on both freeze and the loss of ninja powers so you got enough time to kill him.
Can't wait for part 2 mate.