On the title screen, hold down 'G' and 'H'. Now release 'G' and press fire. After you press fire you can release 'H'. Now during play, whenever you need more energy go all the way to the right, press down on the joystick, and press 'G' (while still in the crouched position). This will refill your life meter. This cheat doesn't work on the A1200 due to the way the keyboard is designed internally.