S.T.A.L.K.E.R.: Clear Sky – standalone prequel for the acclaimed S.T.A.L.K.E.R.: Shadow of Chernobyl, which tells you story about the Clear Sky group, that want to research the Zone and understand it better.
S.T.A.L.K.E.R.: Clear Sky system requirements
Operating System: Windows XP(Service Pack 2)/Microsoft Windows 2000 SP4