Evolution is a real time simulation of the evolutionary process. Creatures have DNA that defines their structure, traits, how they see the world around them, and how they react to it. Each creature is unique, most die quickly, some die a little slower, and others survive (some just like rocks, they usually die too). It is the survivors that reproduce and mutate, just a little, but enough to adapt to their environment. Early creatures are pretty basic but they have the capacity for some pretty elaborate behaviors and, to be honest, I am not sure how interesting this could get.