Small Class for 2D discs, that allows collisions and trajectories to be calculated.
Serves as a visualisation of the stability analysis of elastic 2D disc collisions.
May be improved with 3D spheres, angular momentum and drag down the road.
stable: Discs situated on a line with equal distances smaller than twice the diameter.
unstable: Discs situated on a line with equal distances larger than twice the diameter.
alternating: Alternating small and large distances, which produce a stable fixed point in total.
offset: Discs with an offset producing a stable fixed point.
logarithmic: logarithmic decreasing distances, angle diverges at first and converges at the end.