Initially the puzzle is correctly ordered (at the goal state). Each "shuffle" will randomly shuffle around tiles (10 steps, but sometimes tiles are pushed back and forth). Press "shuffle" until you think it is difficult enough to find the goal state. By pressing "solve" you activate a state-space search for the solution (A* and a clever heuristic based on a summed city-block distance). In the status bar you will see the number of states expanded and the level (number of steps away) the - guaranteed to be optimal - solution is positioned. Pressing "step" will move tiles - step by step - along the search path to the solution. Currently, the applet aborts if more than 1,000,000 expansions are required.

Designed by Mikael Bodén.