It seems the North American release of GSC Game World's shooter prequel has been delayed slightly to September 15th due to unspecified manufacturing problem. The digital download date is also not yet decided.

S.T.A.L.K.E.R.: Clear Sky is a survival FPS game for PC based on a 'what-if' scenario of the second Chernobyl Nuclear Power Plant accident. The game is created as a warning to mankind against mindless play with technologies. S.T.A.L.K.E.R.: Clear Sky is the official prequel to the renowned S.T.A.L.K.E.R. game by the Ukraine-based GSC Game World studio. The game is set in 2011and brings forth the events to have preceded the third campaign of Strelok to the Zone center. S.T.A.L.K.E.R.: Clear Sky introduces an alternative look onto the events of the original game and offers the player to try himself out as a mercenary s.t.a.l.k.e.r. in search of his own path in the world of S.T.A.L.K.E.R.