Video and computer games differ from film and television programs because they are interactive, allowing a player to participate in or even cause events, rather than merely watching them. For many games, however, much of this activity consists of killing human beings--as in Postal, in which the player pretends to be a berserk mass murderer--or indulging in perverse sexual fantasies, as in various pornographic games. Such interactivity can amount to a sort of virtual sin. But the best-selling computer game of all-in fact, the best-selling CD-ROM of any kind, at over 3.5 million copies sold--was created by Christians. Rand and Robyn Miller's Myst has no violence (not even the player has to "lose a life" when making a mistake), nor does it trade on other kinds of morally problematic behavior. Instead, it is a quiet and contemplative game, appealing to both children and adults, which immerses the player in a fascinating imaginary world. And now there is a sequel, Riven. Sons of an evangelical minister, the Miller brothers are avowed Christians, and their values are reflected in both games, which favor contemplation over action and reflection over reflex. The games depict peaceful, yet intriguing environments riddled with enigmas that the player must make sense of. Clicking on to a detail in a landscape may open up secret passageways, leading to strange artifacts the player must figure out how to use. Machines with levers and cranks pique the curiosity and draw the player deeper into the world on-screen. And there is much to explore. Myst's quite astonishing graphics and special effects came on one compact disc. Riven has five. Riven continues the story begun in Myst, about a culture whose "linking books" send their users to different worlds, which are described in the books. Stereo sound and beautifully rendered high-resolution images combine to form a convincing three-dimensional environment that is completely immersive. Attention to detail--both visual and sonic--is an important part of game play, and the puzzles are well-integrated into the storyline. Atrus, a writer of the linking books, asks the player to enter the world of Riven, where his wife Catherine is being held captive by his father, Gehn. The player is also given a book with some of the needed background, but most of what the player needs is learned from directly experiencing the five islands of Riven. Embarking on this adventure, the player comes across clues pointing to the place where Catherine is imprisoned and how to get there, as well as the history of the islands, which figure into the story. Rather than follow a linear storyline, players are free to roam the islands and discover how everything fits together, working a number of machines and seeing an assortment of people and animals along the way. Both Myst and Riven demonstrate the current capability of the CD-ROM as an artistic medium. Although neither is overtly Christian in content, both promote careful observation and thought, and the ability to make connections and put details together to see a larger whole. This is a fantasy that, in our irrationalist age, encourages reason. The world of Myst and Riven--like the real world--may seem strange and mysterious at first, but in the end it is coherent, orderly, and imbued with meaning. According to the Miller brothers, Myst is to Riven what The Hobbit was to The Lord of the Rings. The comment puts them in the tradition of Christian fantasy. Their virtual universe is what J.R.R. Tolkien termed a "sub-creation," made with high technology. Mr. Wolf is a communications professor at Concordia University in Wisconsin.