Instead of building towers and defending against hordes of monsters, play the opposite as an evil mage that builds his army from the ground up to dominate the lands.
Defend the Earth from invading UFOs. Aliens are invading our earth and it is up to you to defend an important nuclear factory. Buy cannons, train new defenders and tell them what to do.
Defend your fortress from the oncoming enemy waves. Place turrets in locations of your choice on your fortress, creating the best defense possible to withhold even the greatest of attacks.
