Vigesimal

Dots, bars, shell

Maya numbers are base-20. A dot is one. A bar is five. A shell is zero — one of the earliest written zeroes in the world. Places stack upward: ones at the bottom, twenties above, four-hundreds above that. The Dresden Codex writes them. Facts and the book itself are in Books.

Write a number

Glyph

5 · 1 · 6 (20s places, top is highest)

Tap a place to add or subtract

×400

×20

×1

Read the glyph

A shell is 0. Count dots and bars, then remember the places.