Adjust the position and velocity of the white ball and start the animation.
Poncelet's Porism is closely related to the trace of a bouncing ball on an elliptical
billiard table.
Here you can study the trace of a frictionless ball on such a billiard table.
The caustic of the traces is a conic confocal to the table itself.
In case that the trajectory is closed the trace forms a Poncelet polygon.
Experiment: Play with the parameters to create various traces.
What happens if the initial shot goes between the foci.