Counter-Strike: Condition Zero was originally planned by Gearbox Software in 2001. It was given to Ritual Entertainment after Gearbox Software met their deadline in 2002. Ritual Entertainment worked hard for the new version of Condition Zero and failed to finish their works in 2003. Ritual Entertainment fall bankruptcy and Turtle Rock Studios resumed their final touches with the aid from Valve Corporation.
Turtle Rock Studios introduced their own version of single-player mission called Tour of Duty modes. The unconnected storyline-oriented single-player missions that were firstly introduced by the Ritual Entertainment were cut and were released as the Turtle Rock Studio's expansion pack called Condition Zero: Deleted Scenes. Since then, Condition Zero is known as a great first step for advanced Bot installment.
Besides advanced Bot installment, Condition Zero introduced HD (High Definition) weapon models and map textures which updated the original Counter-Strike. Some players considered Condition Zero as the 'HD version' for Counter-Strike. Most of the weapons and players model are taken into Counter-Strike Online.