At the cheat menu, press on of the following cheat codes:
| Code: | Result: |
| Up, Triangle, Up, Triangle, Up, Triangle, Up, Triangle. | Alien mode |
| Down, X, Left, Circle, Down, X, Left, Circle. | Infinite ammunition |
| Left, Square, Up, Triangle, Right, Circle, Down, X. | Invincibility |
| Left, Square, Right, Circle, Left, Square, Right, Circle. | Invisibility |
| Right, Square, Up, Triangle, Right, Square, Up, Triangle | Slow Motion |
| Up, Triangle, Down, X, Up, Triangle, Down, X | Xen gravity |
Press Triangle, Square, Left, Right, Circle, X, Up, Down at the cheat screen. Choose the "Extras" at the options screen to load new levels found from other discs, such as the Official US PlayStation Magazine Issue 57 (June 2002) demo disc. To get a bonus level in Decay, get one A in every section. The final level will then become available.
All Decay missionsTo enter the code you must have two controllers.
p2_R3, p1_L3, p1_up, p1_up, p2_down, p2_down, p1_left, p1_right, p2_left, p2_right, p1_X, p1_O, START
Buy a soda from the random soda machines. If you are impatient, shoot the soda machine.
Defeating GonarchThe Long Jump module can be used for more than moving between floating platforms. You can get extra height when you jump into a wall or other object. When you first get dumped in Gonarch's lair, to your right you may see white "plants" coming out of the ground. You can use these as stepping stones to get up on the raised area in the middle. This may not easy, but if you get up there Gonarch will have trouble hitting you with any attacks. It is best to use weapons like the crossbow for this part. You can also use the long jump technique to get to other places you are not supposed to, and it is useful for getting past annoying opponents quickly.
Saving ammunitionDo not waste precious pistol ammo on headcrabs. Use your crowbar, as it is more useful.
Using the pistolUse the following trick to save ammo for all guns other than pistol. Most creatures or persons can be killed with five or less direct shots of the pistol.
Crabs: 2 shots or 1 crowbar hit
Zombies: 4 shots
Electric Aliens: 3 shots
Trip Bomb: 1 shot
Machinegun on stand: 5 shots
Soldiers: 5 shots
Dogs: 3 shots
Spitters: 4 shots
If you have a guard, get him close enough and he will take care of almost anything for you. The only time you ever need to fire is if the creature is close to the guard.
Barney gets cut in halfWhen you enter the room where the lasers are shooting out the walls, run through. There should be a Barney (security officer) on the floor. Watch carefully and you can see the laser go across and literally cut him in half.
Man in blueEnable the "Alien mode" code and start a new game. Go through the hall past the main security room and go straight instead of right. A short way down that hall is the man wearing the blue suit. Use your electric attack to break the window and jump in. If you try to attack the man with the blue suit, it will not work.
Dead guard talksAfter the experiment goes awry, go get the crowbar and come back to the place where the scientist is performing CPR on the dead guard. If you smack the guard with your crowbar, he will talk.
Approach a guard or scientist that tells you information about something. Use a gun that will kill them in one shot, such as the caliber pistol or the crossbow. Shoot them just as you approach them, immediately before they start talking. If done correctly, the guard or scientist will fall to the ground dead, but will still tell you what they originally intended to say.
When you walk around, you will at some point encounter dead scientists, sitting with their back towards a wall. Crouch and then crawl toward the dead scientist. You will glide through him. Continue to walk until you reach the wall, then turn around. You can now see the way the developers have made the skins for eyes and mouth and everything else. You can actually look through the scientist eyes.!
Partial invincibilityWhen in decay mode and are playing both people, the second person is not invincible, even if you enable the "Invincibility" code.
