text: An excellent example system is the "Gaspard–Rice" (GR) scattering system
  —also known simply as the "three-disc" system—which embodies many of the important concepts in chaotic scattering while being simple and easy to understand and simulate.  The concept is very simple: we have three hard discs arranged in some triangular formation, a point particle is sent in and undergoes perfect, elastic collisions until it exits towards infinity.  In this discussion, we will only consider GR systems having equally sized discs, equally spaced around the points of an equilateral triangle.
  Figure 1 illustrates this system while Figure 2 shows two example trajectories.  Note first that the trajectories bounce around the system for some time before finally exiting.  Note also, that if we consider the impact parameters to be the start of the two perfectly horizontal lines at left (the system is completely reversible: the exit point could also be the entry point), the two trajectories are initially so close as to be almost identical.  By the time they exit, they are completely different, thus illustrating the strong sensitivity to initial conditions.  This system will be used as an example throughout the article.