You are a part of US Combat operation. Complete the operation by shooting targets down. You got limited time to complete the entire operation, otherwise you fail.
Enemies are approaching closer and soon they will reach your base. Stop them by strategically placing from defense armies to turret towers in their way.
Click on the empty tiles to the left to construct buildings, use them to defend your base from enemy and to produce units to attack them. All structures are upgradeable, which makes either them or units they produce more powerful.