I am developing a 15 puzzle sliding puzzle game using JavaScript. As half of the combinations in a 15 puzzle is unsolvable I use the formula in __http://mathworld.wolfram.com/15Puzzle.html__ to check the solvability. I am currently adding the option to switch to 8 puzzles (3x3). Are there unsolvable combinations in 8 puzzle too? If so can I use the same formula for it too?