ABSTRACT
A popular type of fl at puzzle, probably familiar to most readers, is one that involves shifting pieces around on a tray without lifting them, to achieve some specifi ed rearrangement-the so-called sliding block puzzles . It is a fairly distinct category, and the published designs are numerous. An excellent book on the subject, Sliding Piece Puzzles by L. E. Hordern , is unfortunately now out of print. An old favorite in this category, fi ttingly called Dad’s Puzzle , is shown in Figure 54 as a typical example. Now nearly a century old, it still rates as one of the best. The object is to start with the arrangement shown, and shift the blocks until the large square moves from the upper left to the lower left corner. It requires 59 moves. In this chapter we will examine some variations on the theme of sliding block puzzles, a few of which are published here for the fi rst time. The fi rst of these, the Butterfl y Puzzle , is notable for its simplicity-six identically shaped pieces in a square tray (Figure 55). The object is to
start with the Monarch butterfl y as shown on the left, and end up with the Swallowtail on the right. It requires 39 moves. But then to put the Monarch back together again may require only nine moves. How can that be possible? This puzzle was introduced at the International Puzzle Party in Helsinki in 2005, made of solid hardwood blocks, with the butterfl ies laminated on in their bright, contrasting natural colors, orange and yellow. The remainder of the puzzles in this chapter might not be classifi ed as true sliding block puzzles, but rather closely related variations. (This confusing matter of puzzle classifi cation tends to be a puzzle in
The Decoy (Figure 58) is one example of a group of recent designs in which polyomino pieces are inserted onto a 5 × 5 tray through an opening in the transparent top (shown in dark gray) and then shifted about until the last piece can be dropped in to complete the assembly. This is one of the more challenging ones of this type, even to get apart. The name comes from the smaller L-shaped opening, which you might assume is for inserting the L-shaped piece. However, it serves no function other than as an access window for moving the pieces about. The solution involves rotation, to facilitate which the corners of the pieces need to be slightly rounded. There would seem to be great potential here for the discovery of many other new and clever combinations of pieces and openings.
