Sliding Blocks puzzles have teased the minds of
children and adults alike for more than 100 years. There is a peculiar fascination in
pushing pieces of wood or plastic around a board to reach a particular position or achieve
a certain objective. Once picked up and started, people find them hard to put down. Many
sliding block puzzles are very easy to solve designed presumably with children in
mind. Some are extremely difficult to solve. However, the fascination does not stop at
merely finding a solution. Especially with the easier type of puzzle, there is much
greater satisfaction in finding the minimum move solution, or in the case of harder
puzzles, a shorter solution than someone elses.
DEFINITION OF A SLIDING BLOCK PUZZLE
A sliding block puzzle consists of a group of pieces of any shape(s) enclosed within a
confined area, in which the purpose is to rearrange the pieces either into a certain order
or to get a particular piece to a specified position. This is accomplished by sliding the
pieces or "blocks" hence the name sliding block puzzles usually one
at a time into areas not occupied by other pieces. The lifting of pieces is never allowed
nor must they hop or jump over other pieces. They must be able to be moved by
themselves i.e. there must be no requirement that they be pushed or pulled by other pieces
as, for example, in railway shunting puzzles. Rotation of individual pieces (without
lifting them) is only allowed if specifically stated. Pieces may be of any shape: square,
rectangular, circular, triangular, Lshaped, etc.
Some puzzles contain obstacles or immovable barriers. Others introduce restrictions:
for example pieces may have to follow specific routes (or lines) and may not be allowed to
stop between points. There may be a requirement that certain pieces may never touch
(orthogonally and/or diagonally) certain other pieces, for example, of the same colour; or
that they do not check (as in chess) other pieces along the same line. In a
few puzzles a piece (or pieces), sometimes of your choice, is not allowed to move at all.
DEFINITION OF A MOVE
There are three possible definitions of what constitutes a move:
(i) Move one piece only in any one direction or combination of
directions. (Under this definition a piece can move around a corner).
(ii) Move one piece only in any one direction.
(iii) Move any number of pieces together as a group in any one direction.
HISTORY AND DEVELOPMENT
No one seems to know when the first sliding block puzzle was invented or produced. What
is certain is that Sam Lloyd made them famous one hundred years ago in the 1870s
with his still well known 1415 puzzle. He did, however, take the idea for this
puzzle, probably from an older French game/puzzle called Le Jeu de Taquain (see
Recreations Mathematiques by Edward Lucas). Henry Ernest Dudeney admitted in his
book Amusements in Mathematics (1917) he took the idea of his puzzle The Four Frogs
from Guarini who produced a chess problem with four knights in 1512. But the movement of a
knight, with its peculiar jump move, can hardly be described as a "sliding
After Sam Loyds 1415 puzzle, many variations of this puzzle came onto the
market, many with designs and pictures but all of them had pieces of uniform size. It was
not until 1909 that a puzzle was patented that introduced rectangular pieces amongst
square ones. There is no doubt that this puzzle is the one that has been most
commercialised, appearing under literally hundreds of names. Barely a year goes by without
some new version being produced. Puzzles in which rotation of the pieces was allowed were
patented as early as 1906. It was the 1920s and early l930s that saw the
explosion in sliding block puzzles and most of those that we have today are descended from
this period. It was not long before non-convex (Lshaped) pieces were introduced into
this type of puzzle and even puzzles with non-rectangular pieces were in circulation
Doublesided puzzles (with one exception) are a comparatively modern development,
limited, presumably because of the difficulty in linking the pieces together so that they
do not fall out. The advent of plastics has now overcome this problem and in recent years
many have appeared on the market.
Also modern are the 3dimensional sliding block puzzles of which I know of only
CLASSIFICATION OF TYPES
For ease of reference all sliding block puzzles have been classified into types as
CLASS A. Pattern arrangement puzzles
These are puzzles that have no set start position, it usually being required only to
muddle up the pieces to set the puzzle.
CLASS B. Uniform piece puzzles
Puzzles in which all the pieces are of the same size and shape, usually square or
CLASS C. Rectangular piece puzzles
Puzzles in which there are square and rectangular pieces.
CLASS D. Non-convex piece puzzles
The same as class C with the addition that one or more pieces will be nonconvex,
most usually Lshaped.
CLASS E. Restricted route puzzles
Puzzles in which pieces can only move along certain predetermined lines.
CLASS F. Rotating niece puzzles
Puzzles in which rotation of the pieces is allowed.
CLASS G. Special shaped piece puzzles
These may contain pieces of any shape e.g. triangular, etc.
CLASS H. Doublesided and double layered puzzles
Puzzles containing either two layers of pieces or containing patterns or symbols on both
sides of the pieces.
CLASS I. Threedimensional puzzles
© 1979 by L. Edward Hordern. All rights reserved.