This is an HTML5 clone of a Java applet available at http://www.hwaci.com/sw/puzzle/ex7.html.
The original website text reads: (accessed 2021-04-05, last modified 1999-08-29)
The object of this game is to move the large square block (the one with the green circle in the middle) to the lower right-hand corner of the board. There are 12 different starting positions that can be selected using buttons to the left of the puzzle.
This game is based on a wooden puzzle named ``The Dirty Dozen'' purchased from a shop near Faneuil Hall in Boston and manufactured by The Square Root Company, 945 Eichler Drive, Mountain View, CA 94040. Neither the puzzle, nor its packaging bore any copyright or patent markings. However, this java implementation of the puzzle is copyright 1996 by D. Richard Hipp.
The Square Root Company has since (circa 2009) developed a web presence at http://squarerootgames.com. They report the following minimum move counts to solve the puzzles:
| Difficulty 1 | 43 Moves |
| Difficulty 2 | 52 Moves |
| Difficulty 3 | 58 Moves |
| Difficulty 4 | 60 Moves |
| Difficulty 5 | 64 Moves |
| Difficulty 6 | 75 Moves |
| Difficulty 7 | 76 Moves |
| Difficulty 8 | 80 Moves |
| Difficulty 9 | 99 Moves |
| Difficulty 10 | 128 Moves |
| Difficulty 11 | 132 Moves |
| Difficulty 12 | 263 Moves |