# PuzzleNation Product Review: Color Cube Sudoku

[Note: I received a free copy of this product in exchange for a fair, unbiased review. Due diligence, full disclosure, and all that.]

Sudoku is one of the most popular pen-and-paper puzzles in the world. It’s found in numerous daily newspapers, puzzle books, and smartphone apps.

After years of tackling regular Sudoku, Extreme Sudoku, Word Sudoku, Mega Sudoku, Samurai Sudoku, Geometric Sudoku, Sum-Doku, and numerous other variations, you’d think the puzzle community at large would’ve exhausted every possible version of Sudoku.

Enter the crafty folks at ThinkFun, who have put a unique spin on another Sudoku variant: Color Sudoku. In Color Sudoku, you have nine colors to arrange instead of numbers.

ThinkFun has upped the ante with Color Cube Sudoku, their latest puzzle-game, by combining the twisty-turny cube possibilities of a Rubik’s Cube with Sudoku-style deductive solving.

It seems like a simple enough set-up. You’ve got a tray and nine multi-colored cubes. Each cube has four of the six possible colors: green, red, blue, yellow, orange, and white. And it’s up to you to arrange the nine cubes in the grid in a 3×3 pattern so that each color only appears once in each row and column.

But that arrangement already introduces complications. Unlike a pen-and-paper puzzle, where you can place any number (or in this case, any color) in any square you choose, the preset color arrangements on each cube limit your choices.

If you need a blue square in the first row, sixth column, given the cubes available to you, you might end up with a second yellow square in your row. Which means, instead of needing a new cube, you need to change one of the cubes you’ve already placed and try again.

What once seemed simple now offers a greater challenge.

But, like many ThinkFun puzzle-games, the more you play around with the possibilities, the more you begin developing new strategies and get into the psychology of the puzzle itself.

Once you’ve placed a few of the cubes, next-level deductive reasoning kicks in, and you can eliminate certain possibilities and begin working more than one step ahead at a time.

For instance, if you’ve placed two cubes in a column, you’ll know you need to change one of the cubes if the third cube will need a green spot in both columns. Since that’s impossible, even without placing the third cube, you know you need to change one of the two you’ve already placed. Which means you’re preventing wasted moves and pushing closer to an actual solution.

Whether you’re tackling Color Cube Sudoku alone or with partners, whether you’re trying to crack a regular 6×6 pattern or taking a whack at some of the variant challenges they suggest — like knight’s paths and other difficult patterns — this is a deduction puzzle that feels like play instead of work.

When I tested this out with a fellow puzzler, we immediately began playing it in a slightly more competitive way. One of us would place a cube, and then the other would place a cube, and we would keep going until no cube could be placed.

You can end the game there, or you can take it a step further, and introduce rules where moving or shifting previously-placed cubes becomes part of the game in order to extend the puzzly gameplay. Heck, if you go long enough, it eventually becomes a race to see who can actually solve the Color Cube Sudoku layout first!

The designers state that there are 2,641,807,540,224 different ways to arrange the 9 cubes, and with seemingly endless variation in such a simple set-up, this is one puzzle-game you can put down and return to numerous times without burning out or feeling like you’ve conquered it forever.

Color Cube Sudoku is available for \$19.99 from ThinkFun and select retailers!

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# Deck the Halls with Loads of Puzzles!

Merry Christmas, puzzlers and PuzzleNationers! I hope you’re having a marvelous holiday!

One of the integral parts of the holiday season is decorating, decking your halls in all manner of festive holiday fun. Whether it’s Santas or garland, mistletoe or sleigh bells, a Christmas village or little dancing reindeer, everyone expresses their holiday spirit differently.

Naturally, around here, we couldn’t resist adding some puzzly flavor to our holiday decorating. I put my origami skills to the test to come up with some puzzle ornaments for the tree my friends at Penny/Dell Puzzles were putting together, and I think the end result was something pretty terrific.

Here’s the tree in progress. You can already see some puzzly touches like a Mega Sudoku front and center there, as well as a wreath on the wall behind the tree!

Let’s take a closer look at that wreath! Darcy did an outstanding job on it, and you can see a lot of flagship Penny/Dell puzzles represented here, like Cross Sums (Kakuro), Codewords, Cryptograms, and Word Games Puzzles!

Here’s a close-up on some of those puzzlier ornaments, including a Crossword star and a Cryptogram crane (one of my contributions) soaring above the Mega Sudoku. (The tree was also liberally garnished with coupon offers!)

A few more ornaments, including a Flower Power grid in the lower left corner!

Here’s the tree in its finished state, all lit up and decked out with gifts. It looks great! The mix of traditional ornaments and puzzly ones really makes for a unique display.

And check out this word search-wrapped gift just waiting for someone! I wonder if the recipient’s name is hidden in the grid! (Maybe they can’t open it until they find themselves!)

Are there any puzzly decorations on your tree this year, fellow puzzlers? Let us know! Send us a picture! We’d love to see it!

Have a terrific holiday!

# The Wide World of Sudoku

[A classic Sudoku grid with a colorful twist, where the 3×3 blue squares also have all 9 numbers inside them. One of many MANY Sudoku variants. Grid from Sudoku-Solver.net]

For more than a century now, crosswords have been the premier pencil-and-paper (or pen-and-paper, if you’re confident) puzzle, but a close second would have to be Sudoku, which has exploded in popularity over the last decade or so.

The simple concept behind Sudoku — a 9×9 grid arranged so that the numbers 1 through 9 only appear once in each row, column, and 3×3 square — is easily modified for any difficulty level, from beginners to topnotch solvers.

The classic form of Sudoku, originally known as Number Place or To the Nines, is instantly recognizable.

[A Sudoku grid from PuzzleNation’s own free Classic Sudoku app for iPad.]

But virtually any set of nine different symbols, characters, numbers, or letters can be used as clues for a Sudoku-style solve. That gives us variations like Picture Sudoku or Color Sudoku, where the same deduction is involved, but the solution is a bit more vibrant.

[A color Sudoku from Aleph.se.]

Word Sudoku follows the same concept, replacing the numbers 1 through 9 with letters, allowing for the added bonus of a 9-letter word reading out along one of the rows. I’ve seen Word Sudoku variations in all sorts of languages, which is neat, because you can still solve the puzzle even if you don’t know the language; you’re simply choosing different symbols.

[A Word Sudoku from Magic Word Square on Blogspot.]

Using letters instead of numbers often factors into larger Sudoku puzzles. While Penny/Dell’s Mega Sudoku is a 16×16 grid using the numbers 1 through 16, other large-scale Sudoku puzzles use letters instead of numbers above 10, while others go so far as to remove the numbers altogether, giving you the option of puzzles that span nearly the entire alphabet!

[A 25×25 monster Sudoku grid using letters, courtesy of colinj.co.uk]

And since we’re already discussing bigger Sudoku puzzles, it’s worth mentioning smaller Sudoku puzzles. Often called Mini-Sudoku or Sub-Doku, these puzzles start at 4×4 grids (using only the numbers 1 through 4) and increase in size all the way up to the standard 9×9 grid.

Those are just the puzzles that use standard Sudoku rules. There are numerous types of Sudoku that add new rules or curious wrinkles to the standard solve.

Perhaps the most famous variant is known as Extreme Sudoku, Diagonal Sudoku, or X-Sudoku, and there’s one crucial difference: the numbers 1 through 9 also appear only once along each diagonal. This additional rule helps with solving, but Extreme Sudoku puzzles often have fewer set numbers in order to keep the difficulty level interesting.

Another popular variation is known as Jigsaw Sudoku or Geometric Sudoku. These puzzles abandon the standard 3×3 boxes, instead using various Tetris-like shapes within the 9×9 grid. Each of these pieces contains each number 1 through 9, and the standard rule of no repeats within a row or a column remains.

These puzzles can either have random shapes or shapes with the same diagonal symmetry that rules both crossword grids and the placement of set numbers in classic Sudoku grids.

[A Jigsaw Sudoku grid from AnyPuzzle.com]

Some variations involve more deduction as well, like Neighbor Order Sudoku or Greater Than Sudoku. These puzzles feature small arrows that indicate whether the number in a given square is larger or smaller than its neighbor.

That’s just the start of math-based Sudoku variants that exist. Sum-Doku or Killer Sudoku uses the standard one-per-row, column, and 3×3 box Sudoku rule, but also adds numerous smaller Tetris shapes and boxes, each with a total. The numbers within that smaller box add up to that total.

Those totals are a crucial aid for solving, since Sum-doku puzzles often feature many fewer starting numbers. (The shapes of the smaller boxes often follow the diagonal symmetry of the set numbers.)

[A Sum-Doku grid from Crossword.Nalench.com]

Another popular variant involves overlapping Sudoku grids. You could have two 9×9 grids that share one 3×3 box, or two 9×9 grids sharing four 3×3 boxes, or you could have more grids overlapping in all sorts of ways.

[A quadruple overlapping Sudoku grid, courtesy of the forums of enjoysudoku.com]

The best known overlapping Sudoku puzzle is probably Samurai Sudoku, which features five 9×9 grids, one at the center and one at each corner, so the 4 corner 3×3 boxes of the center grid link the puzzle together.

Check out this masterpiece I discovered on mathpuzzle.com:

Not only is it a Samurai Sudoku with diagonal symmetry for all the set numbers, but each of the four corner grids operates under a different set of variant rules.

The upper left grid uses Extreme Sudoku (or Diagonal Sudoku) rules, the upper right grid is an asymmetric Jigsaw Sudoku (or Geometric Sudoku), the lower left grid has shaded the location of every even-numbered number to aid your solving, and the bottom right has two shaded ribbons weaving throughout the grid, each of which also includes each number from 1 through 9 once.

As you might expect, there are plenty of variations of Samurai Sudoku. My personal favorite is known as Shogun Sudoku; it’s two linked Samurai Sudoku grids — meaning there are ELEVEN linked 9×9 grids — and there are even larger variations out there for the solver who simply can’t get enough of overlapping Sudoku puzzles.

[Upper left: Tight Fit Sudoku, Upper Right: Thermo Sudoku,
Lower Left: Arrow Sudoku, Lower Right: Consecutive Sudoku.]

Our friends at Penny/Dell Puzzles have several titles that offer a variety of different Sudoku puzzles. The four grids above all appear in various issues of Will Shortz’s WordPlay, all courtesy of Sudoku constructor Thomas Snyder.

You should also check out the Sudoku Spectacular title (featured in our Holiday Puzzly Gift Guide!) as well as their upcoming Will Shortz’s Sudoku title.

I would also be remiss if I didn’t mention the mathier cousins of Sudoku.

Kakuro, also known as Cross Sums, follows the same no-repeats rule of classic Sudoku, but the grids are much closer to Crosswords. The numbers along the top and left-side are the total for each row or column, and they are the primary clues for solving the puzzle. Kakuro rarely features set numbers the way Sudoku does, instead opting for a single filled-in row or column to get the solver started.

[A 6×6 KenKen grid, courtesy of The Math Magazine on Blogspot]

KenKen takes the addition from Sum-Doku and adds subtraction, multiplication, and division to the mix. Each box has a number and a mathematical symbol. The number is the total, and the symbol is how the missing numbers interact to reach that total. For instance, in the upper right corner of the grid, there’s 24X. That means the two missing numbers from that box, when multiplied, equal 24.

And since this is a 6×6 grid, following the same one-per-row and column rules of Sudoku, you know that 4 and 6 are the missing numbers in that box, but you don’t necessarily know where to place them yet.

When it comes to Sudoku, the variations on shapes and layouts are seemingly endless. I’ve seen diamonds and snowflakes, cubes and five-pointed stars, in all sorts of sizes. You can get Samurai Sudoku with 6×6 grids, Jigsaw Sudoku in miniature, and Word Sudoku with Egyptian hieroglyphics.

While researching this post, I encountered this marvelous Sudoku variant, which the constructor calls Star Sudoku.

The numbers 1 through 9 appear once in each triangle, and there are no repeats along any row or slanted column. This puzzle is not only clever, it’s flat-out neat.

So, fellow puzzlers, what’s your favorite variation of Sudoku? Or do you prefer to stick with the classic version? Let me know! I’d love to hear from you!

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