Overview

Counter-Strike: Source (known as CSS), is a modern military multiplayer first-person shooter developed and published by Valve for the PC (via both Steam and retail) on November 1, 2004. The third official iteration of Counter-Strike (after Counter-Strike: Condition Zero), Counter-Strike: Source remakes the original in the then-new Source engine, updating the sounds and graphics while adding a new physics engine (mainly for use with interactive objects, such as barrels). The game also includes minor alterations to the gameplay, such as the removal of ammo purchasing, the removal of riot shields, and the increased effectiveness of flashbangs.
After years of both minor and major updates (including an experimental "Dynamic Weapons Pricing" system in October 11, 2006, the Mac release on June 23, 2010, and a significant update in collaboration with Hidden Path throughout 2010), the game was later superseded by Counter-Strike: Global Offensive.

The beta version of the game was originally released to members of the Valve Cyber Café program on August 11, 2004, then released to owners of Counter-Strike: Condition Zero on August 18, 2004. A new beta version of the game (developed in collaboration with Hidden Path) was released on May 7, 2010 (for those who owned the actual game), including new features and functionality (including 144 achievements, a new domination/revenge system similar to Team Fortress 2, player statistics, and a upgraded Source engine used in Team Fortress 2, Portal, and Half-Life 2: Episode Two).
After tweaking the beta, the features were rolled in to the game on June 23, 2010. Although Valve has closed the beta while rolling in the new features, the beta was later re-opened to test minor updates.