On July 11, 2007, GSC Game World announced a prequel, S.T.A.L.K.E.R.: Clear Sky, which was released on September 5, 2008. The background and some terminology of the game ('The Zone', 'Stalker') is borrowed from the popular science fiction novella Roadside Picnic by Boris and Arkady Strugatsky and the 1979 Andrei Tarkovsky film Stalker that was loosely based on it, as well as Stalker, the film's subsequent novelization by the original authors. The game includes elements of role-playing and business simulation games. The game has a non-linear storyline and features gameplay elements such as trading and two-way communication with NPCs. It features an alternate reality theme, where a second nuclear disaster occurs at the Chernobyl Nuclear Power Plant in the near future and causes strange changes in the area around it. ' S.T.A.L.K.E.R.: Shadow of Chernobyl, previously known as S.T.A.L.K.E.R.: Oblivion Lost, is a first-person shooter computer game by the Ukrainian developer GSC Game World, published in 2007. For other games in the series see the S.T.A.L.K.E.R. This is the first game in the S.T.A.L.K.E.R.
