You are in charge of a small valley on the moon, and it is your job to make sure that no enemy tanks can traverse its path. Now however the enemy is throwing the entire army at the path in an attempt to overwhelm your meager forces. Quickly and precisely place towers to fend off the attack, and as the enemy numbers grow, so must your towers. Upgrade them in both damage and numbers to handle the increased defense, speed and numbers that the enemies begin to possess. Fend off every wave and be heralded as a hero, fail and be the one to let everyone die...