S.T.A.L.K.E.R.: Clear Sky

- Developer: GSC Game WorldMobyGames: S.T.A.L.K.E.R.: Clear Sky
- Publisher: Deep Silver, Inc.MobyGames: S.T.A.L.K.E.R.: Clear Sky
- Platform: PC
- Genre: Action Role-playing (RPG), First-Person Shooter
- Mode: Single-player, Multiplayer
- ESRB rating: (M) MatureMobyGames: S.T.A.L.K.E.R.: Clear Sky
- Release Date: September 15, 2008MobyGames: S.T.A.L.K.E.R.: Clear Sky

S.T.A.L.K.E.R.: Clear Sky is the prequel to the critically acclaimed 2007 first-person shooter S.T.A.L.K.E.R.: Shadow of Chernobyl, produced by the Ukraine-based development team GSC Game World. Despite being released only one year after its predecessor, S.T.A.L.K.E.R.: Clear Sky features a wealth of new content and enhancements including:
1. Upgraded graphics engine with DirectX 10 support
2. Improved enemy A.I.
3. Variety of new locales and enemies
The standalone title is co-published by GSC Game World and Deep Silver, and distributed online exclusively by Steam.
Story

Set one year prior to the events of S.T.A.L.K.E.R.: Shadow of Chernobyl, players assume the role of a mercenary hired to kill Strelok, the amnesiac protagonist from the previous game. Several plot lines will be heavily expanded, and many of the loose ends from the original, including the origin of Strelok, will be directly tied in with the prequel's storyline.
Gameplay

The faction system from the previous game has been given a complete overhaul to give players an increasingly non-linear experience with more gameplay possibilities. Rather than being limited to choosing between Freedom and Duty, you have the option of joining with any of the game's nine factions and rising through the ranks while battling for control of different territories. The weapon and armor system has also been significantly tweaked to allow for unique creations, repairs, and more extensive upgrades in categories ranging from ammo volume to rate of fire. Multi player has been confirmed and will support up to 32 players either online or offline through local area networks. S.T.A.L.K.E.R.: Clear Sky also supports user-created content with its included level editor and a possible SDK slated for future release.