Sliding puzzles are essentially two-dimensional in nature, even if the sliding is facilitated by mechanically interlinked pieces (like partially encaged marbles) or three-dimensional tokens. As this example shows, some sliding puzzles are mechanical puzzles. However, the mechanical fixtures are usually not essential to these puzzles; the parts could as well be tokens on a flat board which are moved according to certain rules.
This type of puzzle has been computerized, and is available to play for free on-line from many web pages. It is a descendant of the jigsaw puzzle in that its point is to form a picture on-screen. The last square of the puzzle is then displayed automatically once the other pieces have been lined up.
How did sliding puzzles became popular?
The fifteen puzzle is the oldest type of sliding block puzzle. Sam Loyd is often wrongly credited with making sliding puzzles popular based on his false claim that he invented the fifteen puzzle. The 15 Puzzle, invented by Noyes Chapman, created a puzzle craze in 1880.
Unlike other tour puzzles, a sliding block puzzle prohibits lifting any piece off the board. This property separates sliding puzzles from rearrangement puzzles. Hence finding moves, and the paths opened up by each move, within the two-dimensional confines of the board, are important parts of solving sliding block puzzles.
