Best free Mac OSX simulation games

A simulation game can belong to a variety of subgenres. In general, simulation games try to faithfully simulate aspects of real life (or, sometimes, fictional reality). There are vehicle simulations in which the player can pilot a car, an aircraft, a submarine and so on. In management simulations, the task involves running a business enterprise, manage a city, etc. In space simulations the player travels the universe piloting a spaceship, trading commodities, fighting enemies.