Move the pointer over the sky: it is a falcon, and the flock flees. The address of the page keeps the settings, to share them.
No leader, no plan
On winter evenings, hundreds of thousands of starlings gather over their roost and fly as one dark, shifting cloud, a murmuration. No bird leads it. In 1986 the computer graphics researcher Craig Reynolds showed how such a flock can steer itself: give each "boid" (bird-oid) three rules, applied only to the neighbors it can see.
Separation: don't crowd your neighbors. Alignment: fly the way they fly. Cohesion: move toward the middle of them. That is all. The shapes of the flock, its waves, splits and sudden turns, appear by themselves. The method won Reynolds an Academy Award, after flocks of bats and herds of penguins in Batman Returns were made with it.
In 2008, physicists filmed real starlings over Rome in 3D and found that each bird keeps track of about seven neighbors, however close or far they are. When a falcon dives, the birds nearest to it swerve, their neighbors follow, and a wave of turning runs across the whole flock faster than any single bird flies. Change the weights of the rules and the same birds become a school of fish, a swarm of midges or a drift of fireflies.