Beat the following modes in order "Training", "Time Trial", "Gun Shooting", "Survival". Note:
Completing each mode will unlock the next mode in the sequence. Then, "Technical demonstration"
mode will be unlocked. Use it to watch the CPU demonstrate its best time with the gun.

  Alternate costume

Beat the game two times using the same saved game location, and getting a different ending both
times. Then, Snake will change into a tuxedo in the elevator during the next (third) time the game is
played. Beat the game once more, and get a different ending. Then, Snake will change into a ninja
costume during the next (fourth) time the game is played.

  Alternate title screen

At the title screen, press the D-pad to change the background color.

  Konami game surprise

Play the game using a memory card that contains a saved game from any prior Konami title
(Castlevania, ISS Soccer, Suikoden, Silent Hill etc.) Then, when Psycho Mantis attempts to read
your character's mind, he will mention various game titles.

  Hint: Defeating Psycho Mantis

Plug the controller into port two and press any button before fighting Psycho Mantis. The word
"Hideo" will appear in the corner of a black screen. Use controller two to fight against Mantis to
keep him from knowing your moves.