In life, uncertainty surrounds us. Things that we thought were good for us turn out to be bad for us (and vice versa); people we thought we knew well behave in mysterious ways; the stock market takes a nosedive. Thanks to an inexplicable optimism, most of the time we are fairly cheerful about it all. But we do devote much effort to managing and ameliorating uncertainty. Is it any wonder, then, asks Greg Costikyan, that we have taken this aspect of our lives and transformed it culturally, making a series of elaborate constructs that subject us to uncertainty but in a fictive and nonthreatening way? That is: we create games. In this concise and entertaining book, Costikyan, an award-winning game designer, argues that games require uncertainty to hold our interest, and that the struggle to master uncertainty is central to their appeal. Game designers, he suggests, can harness the idea of uncertainty to guide their work. Costikyan explores the many sources of uncertainty in many sorts of games -- from Super Mario Bros. to Rock/Paper/Scissors, from Monopoly to CityVille, from FPS Deathmatch play to Chess. He describes types of uncertainty, including performative uncertainty, analytic complexity, and narrative anticipation. And he suggest ways that game designers who want to craft novel game experiences can use an understanding of game uncertainty in its many forms to improve their designs.