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4X is a genre of strategy-based games in which players control an empire and "eXplore, eXpand, eXploit, and eXterminate". Emphasis is placed upon economic and technological development, as well as a range of non-military routes to supremacy. Games can take a long time to complete since the amount of micromanagement needed to sustain an empire increases as the empire grows.

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

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