In the tradition of sliding block puzzles, here is a variation based on a telephone keypad.
Yellow lines mark all of the possible paths between the keys.
After you scramble the keys, your task is to put them back in order. You can exchange a key shaded in green, red keys cannot be moved. In this simplified version of the puzzle, only one key is out of place. Here is the full scrambled version, with all keys randomly placed. 1996-2001 Tekla Inc.