Vi Hart and Nicky Case created a brilliant "playable post" that challenges you to arrange two groups of polygons to make them "happy" by ensuring that no more than 2/3 of their neighbors are different.
What the simulations demonstrates is that a very slight bias against difference very quickly leads to near-total segregation. It's an update of the classic 1971 segregation math of Thomas Schelling.
These little cuties are 50% Triangles, 50% Squares, and 100% slightly shapist. But only slightly! In fact, every polygon prefers being in a diverse crowd.
You can only move them if they're unhappy with their immediate neighborhood. Once they're OK where they are, you can't move them until they're unhappy with their neighbors again. They've got one, simple rule: "I wanna move if less than 1/3 of my neighbors are like me."
Harmless, right? Every polygon would be happy with a mixed neighborhood. Surely their small bias can't affect the larger shape society that much? Well…
(via Vi Hart)