[求助] 一个疑问：《Left 4 dead》（救生之路）开发商到底是谁？

Turtle Rock Studios is a video game developer founded in March 2002 by Michael Booth, later acquired by Valve Corporation. Turtle Rock is involved in the creation of original titles as well as the provision of consulting services to the digital entertainment industry.

Turtle Rock is most well known for their work on Valve Corporation's Counter-Strike franchise. Works include:

An Xbox port of the original Counter-Strike
Counter-Strike: Condition Zero, including the Official Counter-Strike bot
Various maps for Counter-Strike: Source
Currently working on "Left 4 Dead"
On November 20, 2006, Turtle Rock announced Left 4 Dead, a co-operative multiplayer action game. The game will be built atop the most advanced version of the Source Engine and introduces version 2 of Turtle Rock's AI technology. The game is scheduled to debut on the PC and Xbox 360 in November 2008 [1].

On 10th January 2008, Valve Corporation announced that they had acquired Turtle Rock Studios.[1]