Cheat Mode:
Start the game with the 'mgsi.exe -cheatenable' command line. Then press the following keys during game-play
F2: Restore Energy
F4: Unlimited Ammunition (only at certain points)
F5: From Observe Mode Return to Normal view
F6: Observe Mode (camera can be moved throughout Level)
F7: Immediately restart Level with all items already collected
F8 - F12: Toggle alternate Graphics Textures