Time reversibility

Set up an initial configuration as a "billiard table for instance 15 disks in a triangle. Hit the targets with a cue ball and observe the results.

Newtonian dynamics is perfect reversible, but is a computer? Stop the motion after a chosen time and reverse the velocities. What happens as a function of the time delay.

Python contains arbitrary precision libraries, it could be interesting, but difficult, to make the code run with arbitrary precision.

Hint

The easy way to implement this is to inverse the speeds at a multiple of _simul_time, perhaps by modifying the animation code.