The enemy's invading your country from the air. You're going to stop the enemy paratroopers from conquering your country by shooting them down. The paras will try to reach your tower and make it explode. You can eliminate the parachutists that come too close to your tower by throwing grenades. Keep an eye on the parachutes with ammo: make them land safely. You'd better shoot down the boxes with a cross on them, because there's a paratrooper hiding inside!
Use the mouse to aim and to shoot. 1 = gun with unlimited ammo, 2 = rifle, 3 = rocket launcher, 4 = grenades.