Your mission in this shooting-defending game is to protect your base by shooting down the invading enemy aircrafts. Upgrade your weapons, increase your defenses, and defend your base till the end. Use YOUR MOUSE to aim and hold the LEFT MOUSE BUTTON to charge the fire and release to shoot. Holding the squares over a unit for a longer period, will increase the accuracy of the surface to air missile. Maintain the lock until the missile hits. Good luck!