The Laser Cannon is the Protagonist in the Space Invaders series.
The Laser Cannon appears as a wide dome-shape with a peg sticking out of the top where the laser is fired from.
The Laser Cannon is controlled with a joystick (2 buttons in the original release) to move horizontally. There is no vertical movement. A button is used to fire a laser to attempt to hit the descending invaders. The player starts with 3 cannons. A cannon is eliminated if it is hit.