A simulation may be defined as a less complex representation of a source system which is used to inform the user of the source system. Multiple games may be considered simulations or have elements of simulation in them, such as Will Wright's The Sims or Rockstar Games' Grand Theft Auto .
In chapters 7-9 of Unit Operations: An Approach to Videogame Criticism, Ian Bogost defines a simulation as "the gap between the rule-based representation of a source system and a user's subjectivity" in order to highlight the role of the observer putting a narrative onto the simulation (107). He contends that simulations are biased based upon what mechanics have been included or left out in relation to the source system. In the same manuscript, he brings up the controversial nature of simulations as seen in the phenomenon he calls simulation fever.