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Using only symbols available in the "ascii" set of characters

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

Utilizing content created by algorithms rather than human made content. Often utilizes a "seed," a relatively small string that is used to control the randomization algorithm that generates the entire world.

Near infinitely replayable games that usually feature, random generation, perma-death, and brutal difficulty.