A simple simulation of flocking behavior. Between 2 and 96 particles move
in a 3D simulation box. The particles can interact with between 0 and 6
nearest neighbours, with a strength that depends upon the setting of
"correlation". The interaction of one particle with another consists of
them slightly aligning their velocities. This yields typical flocking
behaviour. Try the effect of running a simulation of, say, 50 particles,
changing the number of neighbours and the strength of the interaction.