Over the past month we’ve looked at five different Japanese logic puzzles and their histories.  The amazing international success of some of these puzzles, such as sudoku, kakuro, and nonograms, can only be attributed to extraordinary process of refinement the Japanese puzzle company Nikoli puts its puzzles through.  All of these puzzles have undergone extensive peer reviewing by millions of people, with rules being added or changed, until the puzzle is perfect.  Sudoku is not a success by chance; it is a success because it has been slowly formed over generations, over continents, and finally finished by Nikoli in the 1980’s.

Oddly enough, I was never as much of a fan of sudoku.  I was first addicted to kakuro, or cross sums as they’re sometimes called, in elementary school.  From there I moved on to nonograms, and then to hashi.  I appreciate the commercial success of sudoku, and it is still fun at times, but I enjoy these other puzzles a lot more.  It’s amazing that puzzles such as kakuro and sudoku can be so similar, yet require a completely different way of thinking to solve them.  I would urge you, if you are also not a fan of sudoku, to try one of the other puzzles discussed in this blog, because it may suit your way of thinking better than sudoku.

The beauty of the logic puzzles coming out of Japan today is that their rules are so simple and easy to remember, yet the puzzles themselves can range from being incredibly easy to devilishly challenging.  They all employ numbers, but all are single-digit numbers and the only mathematical skill required for most of them is counting (although kakuro requires adding).  I provided helpful tips throughout this blog for solving these puzzles, but the simplicity of the rules mean that anyone can figure out these tricks pretty quickly.  These aren’t crosswords, where you need a bank of words or cultural trivia to draw from to solve the puzzle; these rely solely on a person’s ability to think logically through all the possibilities and narrow them down to one solution.  Thus people of all ages, of all different backgrounds can enjoy these puzzles.

Hopefully this blog has introduced you to at least one new puzzle and inspired you to try it for yourself.  All the puzzles discussed in this blog can be easily played either online or through an app for free, if you don’t mind the ads.  If you prefer paper and pencil, there are many books and magazines out there.  So the next time you feel stressed about school, work, family, friends, whatever – just take a moment, drink a cup of coffee, and enjoy a simple logic puzzle.  For the last time: happy puzzling, dear reader!

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One last Bryce joke:

My roommate’s best friend Bryce is always buying logic puzzle books for his friends.  People are always asking him, “Bryce, why do you keep giving me logic puzzle books?” and he replies, “Well, someone in this country has to be able to think logically and I’m too busy clowning around.”

 

The last puzzle I’ll discuss is nurikabe, which references a spirit in Japanese folklore that manifests as a wall and is known for misleading or waylaying travelers.  It was developed in Japan by the puzzle company Nikoli in 1991 and has achieved moderate success.  It has also been called Cell Structure and Islands in the Stream.

The objective is simple: create islands of the appropriate size around each of the numbers in the grid.  The islands can only touch diagonally, and otherwise must be completely separate.  Island squares are left blank, while ocean tiles are shaded.  The ocean tiles must all be connected along one continuous path (diagonal connections do not count) and 2×2 blocks of ocean are not permitted.  Each island must have as many unshaded tiles as the number it contains and each island can only contain one number.  Here are some techniques for solving these puzzles:

1. This may seem obvious, but always shade in tiles around any completed islands.  When you first get the puzzle, you can automatically shade in the tiles around any 1 islands.
2. Look for numbers that are only separated by one tile.  For instance, notice the 2 and 4 in the bottom right hand corner of Figure 1.  We know the tile between them must be shaded in, otherwise those two islands would be connected.  We can make similar conclusions looking at that cluster of 3’s, or the 2 and 4 that are diagonally adjacent.  In the former case, if any of the three blank tiles between them was left blank, those islands would be connected, so those squares must be shaded in.
3. Look for ocean tiles that only have one possible path to connect to the other ocean tiles.  For instance, from step 1 the bottom left hand tile must be shaded in.  If the tile directly above it was an island tile, that ocean tile would be cut off from the rest of the ocean tiles.  Thus the tile directly above it must be an ocean tile as well.  We could do the same for the ocean tile that’s stuck between the 2 and 4 in the bottom row.  The tile directly above it must be shaded, otherwise it would be disconnected from the rest of the ocean.
4. Look for islands that have fewer possible orientations.  Consider the bottom 3 in the cluster of 3’s in Figure 1.  We know by step 2 that all the boxes around it are shaded in except the box directly below it; thus that tile must be an island tile.

This should be enough to help you get started.  Nurikabe is a fun and addicting puzzle and I hope you try it.  Below is a link to free online nurikabe puzzles.  Happy puzzling!

http://www.puzzle-nurikabe.com/

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My roommate’s best friend Bryce has an interesting approach to nurikabe puzzles.  People are always asking him, “Bryce, why do you draw miniature clowns in all the blank spaces?” and he says, “It’s honestly the only part of this puzzle that I enjoy.”  When people then ask him, “Then why don’t you just draw clowns and forget the puzzle?” he seems genuinely confused and says, “I’m sorry.  I am just a simple clown and don’t get the joke.”