Half-Life: Sven Co-op Cheats

Load game with the command line: hl.exe -dev -toconsole. Then, press ~ if the orange text on the screen does not disappear. During gameplay, press ~ to display the text prompt and type in sv_cheats 1. Press ~ and enter one of the following console commands..

Note: You can only use cheats when the maximum players is set to "2".

Reach the two first doors one on top of another that you see when you come out the end of the tunnel . Climb up on each other until you reach the top door's floor (or hook up). Click it and it should open. When inside, there is a fun game where you must throw the grenade (there is grenade ammunition in there) into the hole on top and get it inside the glass box.

When you kill enough aliens with the airstrike with only two people on the map at the time, the monsers will spawn out of the ring around the outer area and there will be text reading "Monster revenge".