World's Hardest 15-Puzzle

World's Hardest 15-Puzzle This is a surprinsing version of the 15-puzzle game I found in my great-great-great-grandfather's trunk. Whereas the original 140 years old game has its 15 pieces numbered from 1 to 15 (hence its name), this one has no numbers, all pieces are the same. At first I wondered what kind of joke this was, with its boasting "World's Hardest 15-puzzle"? All pieces are identical, …