The simultaneous publication of Steven Johnson's Everything Bad is Good for You and appearance of media reports of X-rated content in the popular game Grand Theft Auto has renewed controversies surrounding the social effects of computer and video games. On the one hand, videogames scholars argue that videogames are complex, cognitively challenging and emotionally engaging--possibly the most compelling of contemporary popular art forms. Game scholars note how games are transforming government, industry and perhaps now education. Meanwhile, critics claim that games have little redeeming social value and may even be harmful. Even those sympathetic to new technologies are concerned that game players do not understand how games work as simulations. Sherry Turkic wonders if kids playing Sin City are primarily learning simplistic rules such as "raising taxes always leads to riots." To date, relatively little is known about the consequences of game play on the cognition of those who play them, and there are very few studies of "expert" game practice. Questions of how games operate have important implications for the design of interactive learning systems. If a "serious games" market is going to mature, the will be a need for better theoretical models of how games function to produce learning, what kinds of understandings players take away from their games and how these understandings are (and aren't) taken up elsewhere. This design-based research study attempts to answer some of these questions by developing and investigating an after-school program for playing the computer game Civilization III. It offers a model for the design of after-school game-based learning environments and explores the cognitive and affective impact of participation in a gaming community. (Contains 1 figure and 1 table.)