Games that try to simulate real-world activities (like driving vehicles or living the life of someone else) with as much realism as possible. Simulators generally require more study and orientation than arcade games, and the best simulators are also educational.
Items you collect can be constructed from other items or by collecting resources in game. Typically you'll use various recipes combined with the ingredients you find to make new items.
Games that typically contain a large world that you are free to explore in any order you like. Completing objects may open up new areas or change how previous areas functioned.
