Named Game of the Year by over 50 publications, Valve's début title blends action and adventure with award-winning technology to create a frighteningly realistic world where players must think to survive. Also includes an exciting multiplayer mode that allows you to play against friends and enemies around the world.
In game go to console and type map mistake1, if it crashes at the end, load up the game and type mistake2 and then mistake3 after the 2nd map finishes.