The use, by minors, of pinball machines and their variants which are hereby defined to mean any mechanism, spring-loaded or otherwise, which uses a steel ball or similar device to strike bumpers, thereby recording a score or similar record of points or any variants thereof is hereby prohibited, except where accompanied by adult supervision. Adult supervision shall be defined as a person twenty-one (21) years of age or older remaining in the immediate presence of the minor using such machines or games at all times while such games, machines or devices are in operation.