Lintel

you never place an arch. you make one inevitable.

stack blocks in a stone town; each one takes its shape from its eight neighbours, and a gap grows into an arch

Every block redraws itself from its eight neighbors each frame: stacking one cuts a window below, and a gap of air between two stacks gets a lintel across the top, making an arch. You place conditions, not the arch.

Concepts: emergence, cellular-automata, pattern.

An interactive you play with one thumb, on Wundr.