Counter-Strike: Source

Counter-Strike: Source is the sequel to the popular mod for Half-Life, Counter-Strike. It was designed and created from the ground up by Valve Software, using their new Source engine. Counter-Strike: Source features highly realistic physics courtesy of the Havok physics engine, and detailed maps and models. Official maps for Counter-Strike: Source are mostly based on the original Counter-Strike maps, but there are a few new ones. Many were mapped by Turtle Rock Studios, and the rest done internally by Valve staff.