Cheat menu cheats
Effect Code Alien Mode Up, Triangle, Up, Triangle, Up, Triangle, Up and Triangle Infinite Ammo Down, X, Left, O, Down, X, Left, O Invincibility Left, Square, Up, Triangle, Right, Circle, Down, X Invisibility Left, Square, Right, Circle, Left, Square, Right, Circle Slow motion Right, Square, Up, Triangle, Right, Square, Up, Triangle Xen gravity Up, Triangle, Down, X, Up, Triangle, Down, X
Unlock all Decay missions
Go to the Options, then Cheats. To enter the code you must have two controllers.
Effect Password All Decay missions unlocked including bonus mission Xen Attacks 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
Contributed By: Hoaxer87.
Bonus Alien Mission
Get an A-grade on all 9 of the Decay missions. If you successfully do this, you'll get to play a 10th level as a Vortigaunt alien. Getting an A-grade on this level will formally unlock the Alien Mode. (Note: the best way to ensure an A-grade for a level is to get at least 25 kills.)
Contributed By: Cold NRG.
For this code to work, you will need a copy of Playstation Magazine Issue 57 (The one with Jango Fett on the cover) and it's demo disc. From the Half-Life main menu go to option and the the cheats menu. Enter the following cheat: Triangle, Square, Left, Right, Circle, X, Up, Down. It should open an extras menu on the options screen. Go to the extras menu and it should say opening disc tray. When it opens remove the Half-Life disc and put in the issue 57 disc and it should load the Half-Life Uplink Mod. Enjoy!
Contributed By: Bahamut NEO ZERO.
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