Cyan Worlds is currently running a limited time, half price sale on Riven [App Store] for the iPhone and iPod touch.

Riven, the best selling game of 1997, the year of its release, is, as its name suggests, a followup to Cyan’s famed 1993 surreal graphical adventure Myst (which is also available in the App Store [link]).

In Riven, the player resumes the role of the first game’s protagonist, The Stranger. Atrus, author of the linking books that provide access to the various Ages, needs The Stranger’s help in rescuing Catherine, his wife, who is held captive by the evil Ghen in the dying Age of Riven.

Like Myst that came before it, Riven is a point-and-click adventure, but with far more lush scenery and animations. The iOS version of the game features Cyan’s new “Shake-A-Hint" system, that highlights action points to help the stuck player along.

Riven HD, a native iPad version of the game, is expected to be released sometime later.