S.T.A.L.K.E.R.: Clear Sky is actually a prequel, set one year earlier than the events portrayed in the original. In spite of this, the game environment is described by GSC as much more hostile. "Even the air isn't as pure as in the original S.T.A.L.K.E.R. - with these "spatial bubbles" which are like confusing Mobius rings that whole expeditions of Stalkers simply can't find a way out of," said project lead Anton Bolshakov.
The game will be set in the middle of an AI-powered war between Stalker factions. Eight separate factions will be available for the player to ally with, beginning as a raw recruit and working up the ranks. As the player rises through the faction, he will be given increasingly vital missions and take on a central part of the war effort. Players will not be forced to join a faction, although according to reports, the the factional conflict - and presumably the player's role in it - is necessary to move the game's plot forward.
GSC Game World says it is working on improving the game's interface and PDA, as well as improvements in AI and new monsters. The game world will consist of 50 percent new territory to explore, and 50 percent "twisted renditions" of areas presented in the original S.T.A.L.K.E.R. A DirectX 10 version of the game may be available as well, although GSC has not yet committed to it.
S.T.A.L.K.E.R.: Clear Sky is currently scheduled for release in the first half of 2008.