Numero (aka 15-puzzle) is a sliding puzzle that consists of a 4x4 grid of numbered square tiles in random order with one tile missing.
The object of the puzzle is to place the tiles in order from 1 to 15 by making sliding moves that utilise the empty space.
Back in the 1950s in Melbourne, Australia, an inventor named Mr. Richard took the old 1870s wooden sliding blocks game, 15-puzzle, and transformed it into a new craze by creating sliding tiles in a thin hard plastic case.