When it appeared in 1879 as The Gem Puzzle, the 15 Puzzle was accompanied by a cryptic instruction: Place the blocks in the box irregularly, then move until in regular order. At the outset, the applet below shows the 15 blocks in the "regular order". Pressing the "Shuffle" button in combination with the "Cheat" button is a modern day substitute for the block placing instruction. Pressing ether one of the buttons or both of them shuffles the numbers in the box. You move the blocks by clicking in the row or column containing the blank field.

Explanation

Copyright © 1996-2008 Alexander Bogomolny