It shall be unlawful for any operator or proprietor of a mechanical or electronic game to cause, permit or allow same to be located, operated or maintained to be operated within 1,000 feet of the nearest street entrance to or exit from any public playground or public or private school of elementary or high school grades not within 300 feet from any residential zone; said distance to be measured from said entrance or exit in the most direct line or route on, along or across said street or streets adjacent to said public playground or said public or private school of elementary or high school grade or residential zone. The restrictions established hereunder shall not apply to business lawfully in existence and operating upon the effective date of the ordinance codified in this chapter. (Formerly 3.20.020)