In the games in the Sim series (SimCity, SimLife, SimAnt, SimHealth), you try to build a community, an ecosystem, or a public policy. The goal is to make a successful whole from complex, interrelated parts. Tim is 13, and among his friends, the Sim games are the subject of long conversations about what he calls Sim secrets. "Every kid knows," he confides, "that hitting Shift-F1 will get you a couple of thousand dollars in SimCity." But Tim knows that the Sim secrets have their limits. They are little tricks, but they are not what the game is about. The game is about making choices and getting feedback. Tim talks easily about the trade-offs in SimCity - between zoning restrictions and economic development, pollution controls and housing starts.