Cheat mode
Press [Select] at the "Dark Side Of The Moon" menu. Then, press [L], [Right], [B], [L], [R], [Left] to unlock the "Build Secret Base" option. Enter the "Build Secret Base" screen, then press [A] and enter one of the following passwords:
All weapons - Enter "WEAP" as a password.
Unlimited ammunition - Enter "AMMO" as a password.
Invincibility - Enter "GOD" as a password.
200 health - Enter "HEA" as a password.
All keys - Enter "KEY" as a password.
Disable enemy AI - Enter "FRE" as a password.
Full armor - Enter "ARM" as a password.
Enemy on map - Enter "MON" as a password.
Coordinates - Enter "COOR" as the password.