Left 4 Dead 2 is a cooperative first-person shooter video game, the sequel to Turtle Rock Studios's Left 4 Dead. The game released in November 2009.

Left 4 Dead is a cooperative first-person shooter video game with survival horror elements, developed by Turtle Rock Studios and published by Valve.

Half-Life 2 is a first-person shooter video game and the sequel to Half-Life. Developed by Valve Corporation, it was released on November 16, 2004.

Half-Life is a science fiction first-person shooter video game developed by Valve Corporation, the company's debut product.