“The controls consists of an eight way joystick and two action buttons for shooting and jumping. When the character jumps, he curls into a somersault instead of doing a conventional jump like in other games. The joystick controls not only the player’s movement while walking and jumping, but also his aiming. During side view stages, the player can shoot leftward, rightward or upward while standing, as well as horizontally and diagonally while walking. The player can also shoot in any of eight directions, including downwards, while jumping. Pressing the joystick downwards while standing will cause the character to lie down on his stomach, allowing him to avoid enemy fire and shoot low targets. When the jump button is pressed while crouching on a higher platform, the player will drop down to a lower level.
The player’s default weapon is a rifle with unlimited ammunition that can be upgraded into one of four other guns. These can be obtained by destroying the pill box sensors and flying item capsules containing them, or by defeating the red-clad guards in the enemy bases. They consist of a machine gun, a laser gun that shoots a powerful beam, a fireball gun that shoots its rounds in a corkscrew pattern, and a spread gun that sprays bullets in five directions. There are also three auxiliary power-ups that only appear in certain areas when the player is armed with his default gun: a rapid bullets upgrade that increases the firing speed of the player’s shots, a barrier that makes him invulnerable for a limited period, and a bomb that wipes out all onscreen enemies. With the exception of the machine gun and the laser gun, each item comes in the form of a Falcon-shaped symbol marked with a letter representing its function (F, S, R and B).
The first stage is a side-scrolling level where the player is dropped into the jungle and must fend off the enemy’s initial line of defense until reaching the entrance of the first base and destroying the large sensor. Stage 2, as the player must fight his way through a series of passageways before time runs out (a display at the top of the screen shows the map of the base and the time remaining). The player proceeds to the goal by destroying the sensors in each corner in order to shut down the electric current blocking each path. Stage 3 is set in the core of the base, where the player must destroy a set of flashing sensors positioned above him in order to expose the target at the top of the screen and destroy it. Stages 4 through 6 follows a similar pattern to the first three stages, with Stage 4 being a vertically-scrolling level set in a waterfall in which the player must jump his way across various platforms until reaching the entrance of the second base at the top.
The seventh and final stage returns to the side-scrolling format from the beginning, as the player fights his way through the enemy’s final line of defense (which includes a hovercraft, armored trucks, and giant helmeted soldiers) while proceeding through areas such as a snowfield, an energy plant and a hangar, until reaching the alien’s lair, where the regular enemy soldiers are replaced with otherworldly creatures. The player must fight a giant alien head that spawns larvae from its mouth before reaching the final target, a heart that must be destroyed in order to complete the mission.
The player loses a life if player gets touched by enemy or an enemy bullet, fails to complete a base stage before the time limit, or falls into the bottom of the screen when there’s no visible platform. When that happens, he will revert to his default weapon on his next life.