Hold down the '+' key on the key pad and press fire to start the
        game.  Press 'F1' to kill enemies during game.  Press 'F6' to
        refill your energy.  Pressing the number keys gives you various
        weapons.  Another way to activate the cheat is to finish the 1st
        level then on the screen that follows, move the pointer to the
        shield box at the upper left and hit the joystick button and the
        '+' key simultaneously.  Allocate all energy to the weapons.