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

Games with a heavy focus on storytelling and narrative.

Games where the primary goal is keeping the player character alive under harsh circumstances such as dwindling resources or a hostile environment.

Focused on using its text, moreso than its visuals or audio, to tell the bulk of its story/plot. (Still can have great audio and visuals, though!)