The ancient Maya civilization used a vigesimal (base-20) numeral system.
The numerals are made up of three symbols; zero (egg shape), one (a dot) and five (a bar).
For example, 19 is
.... ____ ____ ____Digits are stacked with the higher significant digits at the top, so
.would be read as 1 11 in base 20 (one "twenties" and eleven "ones") or decimal 31.