Genres: First-Person Shooter, Tactical Shooter, Action, Online Co-op / Split Screen, Online Multiplayer, Local Multiplayer / LAN
Release Date: March 1st, 2004
Publisher: Valve Corporation
Developer: Valve Corporation, Gearbox Software, Ritual Entertainment, Turtle Rock Studios
Official Website: http://www.cs-conditionzero.com/
Counter-Strike: Condition Zero is a remaster of the original Counter-Strike with Bot AI, enhanced graphics, and a singleplayer challenge mode. Counter-Strike: Condition Zero Deleted Scenes is a linear single-player game based on multiplayer Counter-Strike's gameplay, with inspiration from Half-Life.

The game was originally announced in May 2001 and was in development by Rogue Entertainment. Later that year, the development company went defunct, so Valve Software handed development over to Gearbox Software, who had prior experience with the Half-Life 1 expansion packs. Gearbox overhauled the game's graphics and models, and worked on implementing several new maps and features (including some which went on to be added to future games), but delays and changes in the plan for the single-player resulted in Gearbox pulling out of the project and the single-player development being handed over to Ritual Entertainment. Ritual converted the multiplayer maps from Gearbox's Condition Zero into 18 unconnected single-player missions, and the multiplayer portion was handled by Turtle Rock Studios, the developers of the Xbox port. The game was expected to release in early 2003 alongside the Xbox port, but critical reception was poor, so Valve assigned Turtle Rock to finish development. The resulting product was similar to Gearbox's version, but contained mostly remade maps from the original game. 12 of Ritual's single-player missions were released as a bundled side-game subtitled Deleted Scenes, with the 6 remaining missions being re-added via updates.

The multiplayer service is still online with user-run servers on Steam, and the Steam version continues to get stability updates along with the other first-party GoldSrc engine titles.