func (sheep *Sheeple) wander(n *lib.SimNode, t lib.Torus) {
	// Move in random direction
	sheep.LastP.CopyVec(n.P)
	sheep.RandSteer()
	sheep.Move(n.P)
	t.Map(n.P)
}
func (b Speaker) Heard(n *lib.SimNode, m *lib.SimNode, t lib.Torus) bool {
	return t.Explodes(b.R, n.P, m.P)
}