Wait until cargo/energy screen appears, move the cursor to the top
 left-hand corner with the joystick, then press fire and [+] on the
 keypad simultaneously. The screen should flash and you will be
 furnished with infinite shields and lives.

 To get to the end of the game, simply go to the outer-most planet.

 [F1]    - Disables enemies
 [F6]    - Replenishes energy
 [0]-[9] - Different weapons