Background. I explore the use in undergraduate classes of active learning situations (ALSs) that model the structure of common pool resources. I respond to critiques of the usefulness of ALSs for use in classrooms by reviewing their ability to convey important concepts and theories and to facilitate student acquisition of policy details.Aim. I examine how learning efficiency is enhanced by choosing the right form of ALS -ranging from abstract games to detailed simulations. The learning efficiency of using games or simulations in the classroom, or something in between, likely depends on the instructor's purposes -conveying general theories applicable to many cases or the details and dynamics of particular policies.Method. I discuss use of a hybrid example of a common pool resource ALS to illustrate use of the ALS to help achieve the purposes of a course on the Rise and Decline of Human Civilizations.Conclusion. Descriptions of the content of debriefing sessions for six courses taught in the US and China provide support for the usefulness of this ALS in achieving purposes that focus on conveying knowledge about abstract features of common pool resource challenges confronting past societies, the climate change problem confronting contemporary global society, and how to avoid tragic outcomes in each case.Rothman (2012) stress the importance of efficiency -the play of games and simulations in classrooms should be circumscribed so that other effective methods of teaching, including lectures and discussions, are not given short-shrift and reduced to levels that obviate their important contributions to the achievement of learning objectives. Ehrhardt (2008, pp. 59-60) also observes that the play of many such games or simulations is divorced from and poorly integrated with the content and purposes of a course. He emphasizes integrating the simulation into the rest of the course material by connecting it to the stated goals of the course as presented across multiple weeks.To ensure a proper fit, Asal (2005, pp. 361-362) stresses the use of simulations to teach about theories that are presented in the course. Simulations can generate excitement about "dry theory" and make theories "clear in a way that lectures and discussions do not." In contrast, Rothman (2012) and Pettenger and Young (2006) emphasize real-world specifics rather than theoretical abstraction. They believe success is related to how well a chosen simulation parallels the complexity of a policy problem and interactions of the actors addressing that problem in the real world.Clearly, tension can exist between introducing, on the one hand, complexity that parallels real-world problems and on the other, maintaining a focus on teaching about abstract and theoretical features of those problems -and using time efficiently to do so. The matter can be resolved, in large part, by careful consideration of the purposes of the course, the time frame available, and a willingness to use a hybrid ALS that incorporates some mix of the features of both games and simulations. ...