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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.

Science-fiction. Commonly including things like aliens, advanced technology, and settings of outer space or distant planets. 

Products that involve or comprise source code, including programming games; does not refer to products with their own source code available, open source or not.