You play the role of Shark, attempting to halt the advance of the Intruders. Your mission is to penetrate deep into their ranks and strike at the heart of the invasion by destroying their Command Centres. Your first task is to defeat their jungle offensive. Extra weapons/ability may be obtained by collecting the weapon packs of aliens you have destroyed. Some troops leave behind their backpacks which contain either a high velocity rifle, a machine gun, or award extra jumping ability, temporary invincibility, or occasionally extra lives. Enemy trucks and helicopters are destroyed by sustained attack. Watch out for drivers and pilots who will try to attack you once you have destroyed their craft.