More of this kind of puzzles:
- online sliding puzzles http://mypuzzle.org/sliding/
- The Complexity of Sliding-Block Puzzles and Plank Puzzles http://groups.csail.mit.edu/mac/users/bob/sliding-blocks.pdf
- How to Make a Slide Puzzle Out of Cardboard http://www.ehow.com/how_12087620_make-slide-puzzle-out-cardboard.html
- SLIDING BLOCK PUZZLES - An Introduction http://www.cimt.plymouth.ac.uk/resources/puzzles/slideblk/sbint.htm
- online game http://www.gamedesign.jp/flash/slidingblock/slidingblock.html
