Level select:
Start the PlayStation with no memory cards. Select campaign mode, then "Load Game". Enter P8H!H!P8P?H!? as a password to unlock all levels in the game.

Enter 48H6HW48H!H!? as a password to unlock all levels under the Recruit difficulty setting.

Level Password
2 4YH8H8PYP?H87
3 WYL8L8XQH?L8Z
4 !YP5P5?QH?P8Z
5 CZT5T5HRF?T8Z
6 KZX5V5PRF?X8Z
7 SZ75Z5XRF?78Z
8 6Z?595?RF??8Z
9 C6DVBVHSF9D9J
10 K6GVFRPSF9G9J
11 S6KVJRXCF9K9J

Other passwords:
Start the PlayStation with no memory cards. Select campaign mode, then "Load Game". Enter one of the following passwords:

H2T8TSHRP!T87
PZX8Z5PRP!Z87
XZ7875XRP!787
?Z?8?5?RP!?87
H6DZDVGSP8D97
P6HZHV48H8H97
X6LZLVWSH8K97

Hidden passages in multi-player mode:
Select the electronics weapons for both players and go to the Hideout. From here, go to the bottom floor and to the large room with the yellow cylinder in the middle. Walk against the inner walls until you enter a large black space. Do the same to the object in the center of the room and hide there from your enemies.