Zeiram Zone

At the main menu, hold Left for three seconds, then press Right. Next, press Circle, Triangle. If you entered the code correctly, the "Option" selection will turn red. Then, enter the option menu to change the difficulty setting to extra hard.

At the main menu, press Down, Circle, Right, Square, Up, X, Left, Triangle. If you entered the code correctly, you will hear a sound. Then a versus mode option will be available.