Start the game with the "mgsi.exe -cheatenable" command line. Then, press one of the following keys during a game to activate the corresponding cheat function:
Result
Key
Restore energy
[F2]
Infinite ammunition, only at certain points
[F4]
Return to normal view from observe mode
[F5]
Observe mode; camera can be moved throughout level
[F6]
Immediately restart level with all items already collected
[F7]
Toggle alternate graphics textures
[F8]
Toggle alternate graphics textures
[F9]
Toggle alternate graphics textures
[F11]
Toggle alternate graphics textures
[F12]
Have Fun!!!