Graph Puzzles Game

Graph Puzzles is a series of logical games. Graphs with a various number of nodes are used as the playing field. Chips with numbers or letters are placed at the nodes of the graphs. The number of chips is one less than the number of nodes. The player moves each time a chip to the empty space from one of the neighboring fields. The goal is to bring the chips in an specific order, either in ascending numerical order or so that the letters represent a word. The target configuration is displayed as a thumbnail. Idea / theory: http://kvant.mccme.ru/1986/07/puteshestviya_po_grafam.htm