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Taking place after a huge catastrophe (eg. man made or natural disaster). See also the more political theme dystopian.

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

A turn-based game mechanic is the opposite of a real-time game mechanic. In a Turn-By-Turn mechanic (synonym), each player has to wait for the other to have played, so that they can play, and so on. This way, each player has the time to think about their strategy. TBT games rely less on action than real-time games.