whatA city of chevrons, some pointing up, some pointing down, thoroughly mixed. Each one is almost easy-going: it only leaves if fewer than a third of its neighbours point its way. Watch the mix curdle into stark districts anyway, with clean borders and no one who ever asked for them. The slider sets the preference; click to stir a neighbourhood back into the mix and watch it sort again.

whySchelling's 1971 model is the classic proof that collective outcomes can betray individual intentions: mild preferences, compounding through everyone's small moves, produce near-total segregation nobody wanted. The slider shows the nonlinearity — below a certain tolerance almost nothing happens, just past it the blocks snap into place.

howAgents of two orientations sit on a grid with a tenth of the cells empty. Over and over, an unhappy agent — one whose like-neighbour share sits below the tolerance — moves to a random empty cell. That is all: no one seeks their own kind, they only leave when scarce among others. The readout tracks the average like-neighbour share, which climbs from one half toward near-certainty, and the length of the border between the kinds, which collapses. When everyone is content the city holds for a moment, then re-mixes itself and sorts anew. Meaning is carried by orientation alone, never by colour. One integer seeds the mix.