Pennant-like sliding block puzzles

After the 1880’s craze of the 15-puzzle (see the previous post) developments lay still for a few decades. The next development was a sliding block puzzle adding larger blocks of sizes 1×2 and 2×2, and enlarging the tray from 4×4 to 4×5. The first such puzzle was patented in 1907 by L. W. Hardy (U.S. Patent 1,017,752, patent granted 1912) and copyrighted on the name ‘Pennant puzzle’ in 1909. The goal of this puzzle is to move the 2×2 piece to a predetermined position on the bottom of the tray.

This puzzle is one of the most widely commercialized puzzles in the world, existing in dozen of variants. Likewise, there are at least seven implementations of this puzzle available in the app store (links redirect to iTunes Store):

• Amber Tiles
• Red Donkey (l’Âne Rouge)
• Block Puzzle
• Kitten Escape
• Path Puzzles
• Sliding Block Puzzle
• Square Master

I have not tried them all. Although these puzzles are not expensive, if I would try all variants of common puzzle designs it would amount to quite some expenses in total! Square Master (illustrated at the left) seems to be the most interesting as far as features and design are concerned. Most of these puzzles seem to restrict themselves to the commercially most widespread variant of all Pennant-like puzzles, using one 2×2 piece and five 1×2 pieces (one of which is put horizontal) with the goal being to move the 2×2 block to the mid centre. This design is originally credited to J. H. Fleming, designed in 1946. Note that Kitten Escape (illustrated at the centre) sometimes uses a different number of horizontal 1×2 blocks.

Taking the restrictions on a 4×5 tray and only using blocks made out of squares, there are actually a lot of more interesting designs around. A nice collection is available at Nick Baxter’s site. Some of the highlights are:

• Super-Century (by Gil Dogon): a classic 4×5 design with only rectangular blocks and with the classic goal to move the 2×2 block to the bottom centre. Number of moves needed: 138.
• D209 (by Dries de Clercq): also only rectangular pieces are used, but one corner of the 4×5 tray is blocked. This raises the difficulty! Number of moves needed: 209.
• Super Dries (by Dries de Clerq): currently the most difficult Pennant-like design known. One L-shaped piece is used, and one corner of the tray is blocked, but the goal is still only defined by the end-position of the L-shaped piece (the position of the other pieces is unimportant). Number of moves needed: 321.
• Picnic (by James Stephens): only four pieces are used, though some are L-shaped and some parts of the tray are blocked. The goal is to exchange two pieces. Number of moves needed: 76

For all sliding block puzzles, the diameter is maximum number of moves between two positions of the blocks. This means that both the starting position and the end position are normally not very interesting. However, using pictures such puzzles could still be made transparent to the user. The largest diameter known for any Pennant-like puzzle is a design that uses the pieces and the tray of Super Dries, but with a different start and end position. The number of moves needed then is raised to a stunning 407!

As a postscriptum I would like to remind all developers of apps for the iPhone that when they want to use any of the more advanced designs they might want to contact the original designers. In most cases these people are not at all unwilling for their designs to be used. Often, they are already satisfied if their name is mentioned with the puzzle.

[Update] They did it again: HuaRongDao [later renamed to “Chinese Sliding Puzzle”] just became available. It’s just the same thing as the above. I hope this quote from their description of the game is supposed to be ironic (though I doubt it):

Game Background: Not sure this game was originally from China. But the figures on the blocks come from the well-known Chinese historical story “The legend of three Kingdoms”.

It’s not from China! This is a typical example of a story to sell a game (and many puzzles are preferably sold using Chinese themes—I’ll have more to say about that later in the discussion of Tangram).

[Update 24 November 2008] It’s unbelievable! Somebody takes another try at it: Knights and Dragon. That is number 10. Ten times basically the same puzzle in the app store. Well, that’s an easy way to get to 10.000 apps in six months!

[Update 10 December 2008] I won’t say anything anymore: Box:Out!

[Update 27 March 2009] It has taken some time for the next version to appear, but here is number 12: Treasurehunt.

[Update 8 April 2009] HuaRong is a different implementation from the earlier mentioned HuaRongDao, but it is of course basically the same thing.

[Update 16 April 2009] Doesn’t look like it at first, but it is definitively a classic Pennant puzzle: Save Her.

[Update 21 April 2009] Aargh! Again somebody forgetting history. This puzzle is a classic Pennant design, but no mention whatsoever of L.W. Hardy.

[Update 31 May 2009] Another cover story that I had never heard about: Khun with reference to an old Thai poem. The link to pennant puzzles remains a bit enigmatic.

[Update 3 July 2009] The classic once again: L’Ane Rouge.

[Update 16 July 2009] A bit of exaggeration is often useful in marketing, but you know better: Dad’s Puzzle has indeed “been around for over a hundred years”, though only by a small margin!

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