Note: The following trick requires a disassembled Atari joystick in order to activate two opposite directions at the same time.

Go to the left side of the screen, hold Up + Down and then hold Right. As soon as your character begins to move, press Fire. Note: You should be holding the three directions while pressing Fire. The bullets will start from the center of the screen and continue to the right. This is useful if there is a wall in the center and there are robots that you want to hit. Press Left instead of Right when all three directions are held causes bullets to leave from the guy's head.