“…It would be natural to consider the particle moving in the quantum realm [7,37,39] or moving relativistically [11,12,13]. Other billiard systems consider modifications to the region of motion itself, for example, a hole or multiple holes within the region-these are the so-called "open billiards"; billiard systems where the boundary changes in time [18,19,21,24,25,26]; and billiard systems where the billiard moves under the influence of a constant force field, either magnetic [3,10,14,30,38] or gravitational [9,20,23].…”