Aliens have come back after being defeated the first time. This time they have genetically altered themselves with acid blood. This blood can hurt your defense so do everything possible to keep them as far away as possible. Use your mouse to make crop circles that the aliens must follow in a path in order to try to get at the farmers. Then place your towers in the tall corn and attack them as they start walking through the corn circle maze. Use all of your strategy to best take down the waves as they get tougher and tougher. Upgrade your defenses in order to get ready for the toughest waves.