Try doing that with a single set of top-level rules, said Langton. The system would be impossibly cumbersome and complicated, with the rules telling each boid precisely what to do in every conceivable situation. In fact, he had seen simulations like that; they usually ended up looking jerky and unnatural, more like an animated cartoon than like animated life. And besides, he said, since it’s effectively impossible to cover every conceivable situation, top-down systems are forever running into combinations of events they don’t know how to handle.
