Counter-Strike: Condition Zero (Gearbox Software design), Counter-Strike Wiki

The version of Counter-Strike: Condition Zero designed by Gearbox Software was the second of four major iterations of the game in the game's convoluted development history. This iteration of the game was originally more reminiscent of the version of Condition Zero developed by Turtle Rock Studios, having an arcade-like take on the single-player experience. Later during development, the design for the single-player component was changed and it became more similar to the version designed by Ritual

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