- Joystick: Use the joystick to direct each player through the stages. Press left and right to make the player run in either direction. Press up to aim the player's gun upward. Press down to crouch low. Press the joystick diagonally to aim your weapon in those directions.
- Fire: Press the fire button to shoot your current weapon. Your weapon will fire in whatever direction the joystick is being pressed (unless you are crouching on the ground.) To fire straight down, you must hold the joystick down while jumping.
- Jump: Press the jump button to make each player leap off the ground. They can jump straight up, or to either direction. Hold the joystick down while pressing jump to move your player down to a lower platform.
- 1 or 2 Players: Press either button to begin a one or two player game.
Throughout the game, you control Bill and Lance, two battle-hardened marines who are dropped behind enemy lines in a dangerous attempt to invade an enemy base and sabotage all operations. Player 1 always controls Bill "Mad Dog" Rizer (shown left, based on Arnold Schwarzenegger, named after actors Bill Paxton and Paul Reiser from the movie Aliens.) Player 2 always controls Lance "Scorpion" Bean (shown right, based Sylvester Stallone, named after actors Lance Henriksen and Michael Biehn from the movie Aliens.) Other than their names and appearance, both players are identical.
Bill and Lance are familiar with the use of a variety of weapons. They begin each new game, and every new life, with a standard rifle. They may only use one weapon at a time, and they automatically switch weapons as soon as they touch a new one, with no ability to switch back to the weapon they previously possessed. Bill and Lance can shoot each weapon in eight different directions, and they cannot harm one another. They are very athletic and are capable of jumping very high into the air. They may also fire their guns while jumping.
Bill and Lance must survive the assault on each stage, and arrive at the end where they typically face a powerful boss. The boss must be defeated before Bill and Lance can advance to the next stage. They each begin the game with many lives (usually 3), and lose one every time they are touched by an enemy, bullet or explosion. When both players are out of lives, the game ends. Each player may continue up to three times by inserting more credits. Any attempt to continue beyond the third will result in the game starting over from the first stage.