a little demo in go using the ebiten game engine
vaguely follows my memory of how flocking algorithms work. Every so often each gopher picks a new target point and accelerates towards that. New target points are randomly distributed around a central point. To prevent the flock heading offscreen the central point is a weighted blend between the centre of the screen and the centre of gravity of the flock, with the weight set by how far the flock is from the centre of the screen. A simple proportional, differential, integral control algorithm is used to set the acceleration. The current weights are underdamped so the gophers bounce back and forth a little (ringing) before reaching the target.
