One of the most fancy and cutting-edge applications of computer technology is in the building of simulations that emulate the behavior of real-life or theoretical systems or situations. Such simulations can serve a variety of purposes such as training and education, research, and entertainment. To take an easy example, certain experiments in psychology or behavioral sciences are either unethical or impossible to conduct--for instance, the assessment of how a particular person would react given certain accident situations often cannot be known well using standard means because accident situations cannot be created at will. The military may wish to train its soldiers in war, but does not wish to needlessly expose them to the actual bloody horrors of battle. A pilot may need to be trained to fly a new type of aircraft, but there is little sense in risking the plane and her own life during the training...