Play Left 4 Dead

Four survivors, the AI Director and a chainsaw; co-op zombie shooting at its best.

Play Counter-Strike, a popular first-person shooter game known for its competitive gameplay and team-based strategy.

Play Counter-Strike 2, a popular first-person shooter game

Nine classes, hats and the Heavy; Valve's cartoon shooter, free since 2011.

Valve remake the Quake mod on the Half-Life engine in 1999, nine classes and concrete bases intact.

The retail release with a bot ladder and Deleted Scenes, a single-player campaign cut from another studio’s version.

The 2004 port to the Half-Life 2 engine: physics, ragdolls and an argument about de_dust2 that lasted a decade.

The version that made the game an esport and the skin economy that came with it.