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

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 computer game by Ukrainian developer GSC Game World.[3] The game consists of a roughly 50/50 mix of new areas and old, remodeled areas from the previous game. Source: Wikipedia, "S.T.A.L.K.E.R.: Clear Sky," available under the CC-BY-SA License.