Eliminate the paratroopers invasion by shooting down paratroopers, choppers and armored vehicles. Don't let them land, or your gun will be bombed.
Mouse to aim and shoot. Press 1-3 to select different guns. Press 4 to select a grenade.
Use guns to shoot down troopers, choppers and armored vehicles. Use grenades to kill landed soldiers. Four soldiers from one side will bomb the gun.