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Thomas Schelling's segregation model is one of the clearest examples of macro-patterns emerging from modest individual preferences. Nobody needs to prefer total separation for separation to appear.
Each occupied patch is a blue or orange household. It counts occupied neighbors and same-color neighbors, marks itself satisfied when the same-color share clears the threshold, and otherwise moves to a random empty patch. The stochastic relocation keeps the model compact while the neighborhood counts expose the sorting pressure directly.