High Quality Content by WIKIPEDIA articles! S.T.A.L.K.E.R.: Clear Sky, is the prequel to S.T.A.L.K.E.R.: Shadow of Chernobyl, a first-person shooter video game by Ukrainian developer GSC Game World. The game consists of a roughly 50/50 mix of new areas and old, remodeled areas from the previous game. The X-ray graphics engine has been updated to version 1.5 and includes DirectX 10 support (later patch 1.5.06 included DirectX 10.1). Additionally, the AI received an overhaul to accommodate the new faction wars feature.