You're introduced to a new main character and several new mechanics, the most important of which is factional gameplay, which allows you to ally with an AI-controlled group and assault its enemies.
This isn't a full-fledged follow-up, but rather a stand-alone expansion set before the events of the original. Clear Sky offers a few improvements and a number of issues, but the real star of the series-the large, barren wasteland created by a fictional explosion of the infamous nuclear facility in Chernobyl, Ukraine-is still the most impressive aspect of this prequel. The Zone isn't a friendly place, and if you played last year's shooter/horror/role-playing hybrid S.T.A.L.K.E.R.: Shadow of Chernobyl, this comes as no shock.
