Enter the options screen. Set "Vibration" to "1" and "Sound Effects" and "Music" to "0". Then, hold L1 + L2 + R1 + R2 + Circle + Square. If you entered the code correctly, the message "Spooky Cat" will appear in the middle of the screen.
Successfully complete the game on the hard difficulty setting to unlock a bonus helicopter and the "Maniac" difficulty setting. The bonus chopper flies faster, turns faster, ascends/descends faster, the front-mounted cannon fires faster and takes longer to overheat and cools faster, and the rotor sounds a little different. Successfully complete the game on the "Maniac" difficulty setting to unlock another bonus helicopter, which you can use on any difficulty setting. It has the same top speed and fire rate as the other bonus helicopter, but more armor.
|Master Code (Must Be On)||EC878280 1449D2E4|
|Infinite Armor||4CC1D49A 1456248F|
|Infinite Ammo Weapon 1||4CD5B248 1456E788|
|Infinite Ammo Weapon 2||4CD5B24C 1456E788|
|Infinite Ammo Weapon 3||4CD5B250 1456E788|
|Never Overheat||4CC1D48C 1456E7A5|