It's been over one hundred years since the first 9x9 magic square puzzles started to be published in newspapers, though the name Sudoku has been in use for just about 30 years. Countless variations have been invented and refined - some crazy difficult, others much more accessible to the masses. The Sudoku variation I've discovered recently is definitely for the more casual puzzle aficionado, but can still offer some challenge for the seasoned puzzler.

5x5 Sudoku is just like what its name suggests. Unlike a classic grid of 9x9 cells, this new variation has a length of only 5x5 cells. The grid is divided into five subsections, or regions, with a central cross, resulting in a visually appealing symmetry.

The paperback book, authored by Christopher Thomas, is nicely presented with 200 puzzles, each page containing one single large square with a puzzle. However, with a more economical approach, the book could've easily featured 800 puzzles in it. A suggestion for later volumes in the series. I can understand the design choice, though, as you are able to concentrate easily on one puzzle at a time. As this is the first of several planned books, you'll start slow and easy. Expect a higher challenge in the coming volumes. Solutions for each puzzle are provided at the end of the book.

Like any other Sudoku puzzle, you start with a partially completed grid with eight numbers neatly and sparsely placed on the grid. A well-trained eye will surely notice the well planned symmetry of the starting numbers, as if a beautiful mathematical dance was being carried on between the puzzle and the solver. Only one solution per puzzle is possible.

I've solved almost half of the available puzzles, so far. Even though they're easily solvable within 5 minutes or less, this variation is really fun. With less numbers to think about (you only use numbers from 1 to 5), and with a less crowded grid, you'll breeze through the 200 puzzles in no time. Maybe those 800 puzzles wouldn't be so bad, after all...

You'll find on the photos that I've not written on the book. I personally don't like to write on the books. I've even made an Excel file on my phone specifically for this book so as to not spoil it. You can also do the puzzles on a paper notebook or something, if you also don't like to write on your books. In the end, you'll find that you can reuse the book and solve all the puzzles again whenever you like, since there are no marks on it that prevent you from doing so again and enjoy it a second, or third, or how many times you want. You can even lend it to a friend. Just don't forget to tell them not to write on it...

I have no specific strategies to solve a Sudoku puzzle. But then again, I'm a casual when it comes to Sudoku. I like to take my time and discover how to solve the puzzle on my own without thinking too much about special tactics and strategies. I've been playing it for years, and that's how I intend to keep doing it.

Closing Comments:

I was pleasantly surprised by this new Sudoku variation. It's a simple and yet addicting puzzle, great for a short break from your daily life. If you like the classic Sudoku, you're gonna love the 5x5 Sudoku. Can't wait for the next volumes.

Availability: You can find the 5x5 Sudoku vol.1 on Amazon for just £6.99.

Deducktion, another clever design by Raf Peeters and produced by SmartGames, is a logic game where you can play with numbers in a fun way, and it's also very educational for the young and growing minds. If you like mathematical puzzles and games, keep reading to find out how it works.

The game is nicely presented in a notebook style with clasp. Inside you'll find two sets of booklets with 48 challenges on the left, divided by four difficulty levels -- could've been more, but it's enough to get you busy for a while -- and a magnetic board with 12 duck magnets on the right. The ducks are grouped in three families, each color representing one family comprised of a mother duck and its corresponding ducklings. There's a 3x4 grid which shall be filled entirely by the 12 ducks, although there are some rules to take into account before you start:

- When starting a challenge pay attention to the numbers and colors on the squares.

- There can be an isolated number without a specific color, or just a color, or even both (more common on the starting challenges). These squares can indicate that a specific duck with that number should be placed on that same square, but may not indicate its color, or the opposite, where you are given the color but not the actual number - You have to figure out for yourself. If there's a square with a color and a number, no "deducktion" is necessary - it's that specific duck.

- Each duck family must be placed on the board in a chain. This chain may not be straight, but the numbers do have to be adjacent (for example, you can't have duck #4 next to #2 and so on). The chain needs to have the correct number sequence (horizontally or vertically).

The logic behind this game reminds of Sudoku, because you have to use strategic planning and deductive reasoning skills. Since I love Sudoku so much, it's easy to understand why I also enjoyed Deducktion. The subtle but creative way that the designer found to have bigger and smaller duck families allows you to find the correct logic in every challenge to solve them (green family has only three ducks; red family has four and yellow family has five ducks). You'll have just the necessary information to solve all 48 challenges.

Closing Comments:

Deducktion is one of the most educational games you can find in the SmartGames catalog. It's a great tool to exercise your brain, whether it's for a growing 6 year-old or a 66+ year-old that needs to keep their brain as sharp as possible. If you know anyone that can't have enough Sudoku puzzles, this is a great gift for them.

Availability: Amazon is your best bet to find the Deducktion game or any other by SmartGames.

Today's puzzle is a classic dating back from 1933. The Calibron 12 is a fascinating packing puzzle invented by Theodore Edison, son of Thomas Edison. The original copy can be seen in Jerry Slocum's collection.

Suggested by its name, the puzzle is a selection of 12 rectangular blocks with different sizes that need to be placed inside the provided frame. There are two identical pairs of pieces, though. Sounds easy enough, but it's actually one of the hardest packing puzzles I've tried so far.

The Calibron 12 is beautifully presented in this 18 x 23cm (7" x 9") stylish frame with an extra space for a piece so that it comes unsolved. The pieces are a mixture of four different types of precision cut woods, resulting in a unique combination of colors from a wide selection used at Puzzle Crafthouse's shop. Each piece has its own relative size engraved, so it's very easy to identify them and see the size relationships between them. It can also prove quite helpful in a mathematical analysis.

The packing area measures 16 x 16cm (6.3" x 6.3"), which corresponds exactly to a square measuring 56 x 56 units. It's also known that the total area of the pieces is 3136 units. Knowing the relative size of each piece you have all that it's needed to solve this problem mathematically... If you can.

(Click to Enlarge)

I got this puzzle a few weeks ago and up until the time of writing, I'm yet to find a solution. In fact, there is only one possible arrangement for the blocks that can fit the 56 x 56 frame. There are other theoretically possible rectangle areas, like 112 x 28, 64 x 49 and 32 x 98, however they can't be solved with these particular pieces. This may be a challenge for you to see which piece sizes would be needed in each rectangular area. With fewer pieces you can make many smaller rectangles and attest that the blocks have all kinds of possible combinations and arrangements. Finding the correct one, well, that's a whole different mater.

The puzzle is rated as a 5/5 level of difficulty, and I couldn't agree more. Although perfectly possible, I believe it's extremely difficult and unlikely to find the solution just by randomly packing the pieces. Unfortunately, I'm not a math wiz, so tackling the problem by mathematical analysis is out of the question. I read an interesting article explaining the methods for packing different rectangles in a frame, but for a layman it's not easy to wrap your brain around it. I will continue and try to find the solution the old fashion way. I reckon if I'm persistent, I'll eventually find it... Or not.

Closing Comments:

Even though I'm yet to find the solution for the Calibron 12, I love it! It's a simple, but brilliant concept, and the way that it's presented makes you want to try it, even if you don't dominate the math field. If you're a math geek, this is the perfect puzzle for you to put your skills to the test.

Availability: This particular version of the Calibron 12 can only be found at Puzzle Crafthouse and it's available for $27 USD.

Today, I'm going to describe the fourth puzzle from Roscreative, the Rudenko Doser, designed by Valery Rudenko (English). Check out the three previous reviews here, here and here. Only one left...

The Rudenko Doser is unlike any other puzzle you've seen. This very original design reminiscent of an hourglass is based on the task of mathematician Siméon Poisson for measuring liquids. There are three vessels: the main one is connected to the two smaller vessels with taps to open and close the flow of "liquid" (represented by a green sand-like material). The puzzle is double-sided, as the smaller vessels are marked with capacities of 5 and 3 liters on one side and 7 and 5 liters on the other. There's also a tap between the smaller vessels to pour "liquid" from one to another.

(Click to Enlarge) - Hard Side

As mentioned above, there are multiple tasks for you to try and solve, more specifically, three on each side: On the easy side, with marks for 5 and 3 liters, you have to successfully measure 2, 1, and 4 liters; On the hard side, with the 7 and 5 liters, you need to correctly measure 3, 4, and 1 liters. These number sequences are in order from easier to harder. Also, note that the marks are just representations of the actual measurements, as the puzzle is relatively small, at about 9 x 9cm (3.5").

Solving the puzzle's challenges is not that difficult, even the ones on the harder side. Most of the tasks require multiple dosages in each vessel to get to the desired measurement, so the hard part might be to plan in advance how you will distribute the "liquid" back and forth. As an example, I'll describe below one of the easier tasks for you to get an idea on how to solve them, but the other ones follow the same exact logic, only lengthier.

(Click to Enlarge) - Both Vessels Full

So, one of the challenges is to accurately measure 2 liters with the 5 and 3 liter vessels. The first step is to completely fill the 5 liter vessel. When you're done, rotate the puzzle counter-clockwise by 90º and open the green tap, the one between the two smaller vessels. This action will allow you to fill the 3 liter vessel, leaving the rest of the "liquid" in the 5 liter one. What you see left in the 5 liter container is the exact measure of 2 liters. The other challenges won't be that simple, though, but still solvable within 5 minutes each. It took me less than half an hour to solve all six tasks.

Video: To have a better idea of how the puzzle works, check out this video with Mr. Rudenko.

Closing Comments:

If you loved mathematics related tasks or computer science projects in school, then you're certainly going to enjoy the Rudenko Doser. What I liked most about it was the hourglass appearance - It's definitely quite a unique design. Be careful when maneuvering the puzzle, though, as it tends to shed some of its green sand particles here and there. Nevertheless, it's a great looking puzzle and I can surely recommend it to any puzzle enthusiast.

Availability: You can buy Rudenko puzzles at Hendrik Haak's Puzzle Shop, from Germany or Labirint.ru in Russia (English translation here). For wholesale, contact Roscreative directly.

Now available on PuzzleMaster as well.

Links: 

English translation of Rudenko Doser's page

English translation of Roscreative website

Russian Magazine Article about Valery Rudenko (English Translation)

Russian Newspaper Article about Valery Rudenko (English Translation)

Lately, I have been fortunate enough to have tried some of the most amazing puzzles, since I started collecting them, back in 2008. The latest addition to my collection is the Quadratum Cubicum, which was entered at last year's 31st IPP Design Competition.

The Quadratum Cubicum is a group of nine square trisection puzzles, ranging from six to nine pieces, that essentially, turn a bigger square into three identical smaller ones. Christian Blanvillain was the one responsible to group together the eight best solutions from past mathematicians and turn them into a unique puzzle.

As you might have have noticed, I mentioned that there were nine solutions in the Quadratum Cubicum, but only eight were chosen. That's because the remaining one and most recent solution, was discovered by Christian himself in 2010. His solution, however has a particularity, as it's the first one proposed, that has all its six pieces having the exact same area. One of my favorites, because of its elegant symmetry.

In history, there have been many examples of how to cut a square into three identical squares. Abu'l Wafa' was the first one, in the tenth century, to have come up with a solution to this problem, with nine pieces. Also, one of my favorites. To know more about the history of the square trissection, visit this page.

Others have followed since Abu'l's solution. Nobuyuki Yoshigahara, the famous Japanese puzzle designer, known for his many Hanayama Cast design contributions, have also discovered one solution in 2003, with nine pieces and actually, the only one with the same piece arrangement for the same three squares. Curiously enough, it was the hardest one for me to solve. Another notable mathematician, the French Édouard Lucas, famous for inventing the classic Tower of Hanoi puzzle, also proposed his solution in 1883, a century before I was born.

The puzzle is presented in a beautifully made wooden box with pin-lock, measuring 18.5cm x 18.5cm x 3.5cm (7.28" x 7.28" x 1.38"). Inside, comes with the nine solutions, with its 68 pieces, all built in plexiglass. The material chose for the pieces looks very appealing, although after some use, you might see them covered in fingerprints. A good wipe with a microfiber cloth will make them as new, though.

One thing that I appreciate the most in puzzles, and very few can provide it, is the variety of challenges that you can try and solve with them. The Quadratum Cubicum is fortunately, one of such examples and throws at you a few of them, with different levels of difficulty.

With the 68 pieces of the nine solutions combined, there are four sizes of squares that you can build: 1 large square with 42cm (16.53") in length; 3 medium large squares with 24.2cm (9.53") in length; 9 medium small squares with 14cm (5.51") in length and finally, 27 small squares with 8.1cm (3.19") in length. By the way, the logo on the box, cleverly shows this notable relation between the square sizes and numbers.

The puzzle already comes with its nine solutions, solved into their medium small squares, although by no means, it will make things easier for you. The first challenge that you can try to solve, in order to become more familiarized with all the solutions and try for the bigger square, is to solve each of the nine solutions, into its smaller three identical squares. When you turn all nine solutions into smaller squares, you'll be left with 27 squares. By stacking them on top of each other, you can build a cube with exactly the same height as the length of a small square, since each piece has the thickness of 3mm (0.12"). This cube is simply called the Cubicum.

After you've solved the solutions into the 27 squares, you can try next to solve them into their original squares, one at a time. Some of them will be easy, but you'll find others much more tough. The ones I found the hardest, were the Nobuyuki Yoshigahara's and the Edouard Lucas'.

Building the next larger three squares, even though its counter-intuitive, is actually much easier, because you just have to place nine smaller squares from three solutions, side-by-side in a 3x3 grid.

On the other hand, building the larger 42cm square, is the hardest challenge. In principle it's easy to build it, because like the above example, it uses all nine 14cm squares in a bigger 3x3 grid. The hard part, however, is to solve it. By mixing all 68 pieces, it becomes extremely challenging to recognize which piece belongs to what  solution. That's why, in order to successfully solve it in a good time frame, you have to know most of the nine solutions by heart. It took me almost a whole afternoon to finally have the biggest square built.

The first three or four solutions were relatively easy to solve, because their pieces were easily recognizable, but the rest were quite challenging and given the fact that some had very similar pieces, complicated things much more. Slowly, with time, I got to finish another two or three solutions and, as the number of pieces got progressively smaller, so it became less complicated, until with much relief of mine, there was only one solution left. I had finally conquered the ultimate Quadratum Cubicum challenge.

When you're done with the Quadratum Cubicum challenges, there are a few more that you can try to solve. Building a rectangle, using the highest number of pieces that you can and without using any of the nine solutions, is probably the most interesting one. But there are more... Visit this page to know more.

Picpulp, the company that builds the Quadratum Cubicum, has a few other designs presentations for this puzzle, that can fit anyone's budget. Other than the Collector's Box you see in this review, there's another one, also with the nine solutions, but with the box format of the Cubicum, the cube with the 27 squares. You can also get a box with just three solutions of your choice, or if you prefer to just try a single solution, there are more affordable options. Finally, if you have one of the three boxes with three or more solutions and want to solve one solution at a time, you can get a separate tray, just for this task.

From the history behind the solutions, to the actual presentation and build quality of the puzzle and the variety of challenges, Christian Blanvilain's Quadratum Cubicum is a very special addition to any puzzle collection, and the different levels of difficulty, as well as the varied purchasing options, sure makes it accessible to anyone, puzzler or not.

I haven't been so immersed in a puzzle for quite some time, for the Quadratum Cubicum is the dream puzzle of the packing and dissection fans and most importantly, it's like owning a mathematical treasure.

(Click to Enlarge)

The Math Snake is a Puzzle Crafthouse exclusive design, in collaboration with Ken Irvine, who wrote the program for the block layout.

There are two versions. One with only 7 blocks, with 1024 possible permutations, and the version I have, with 9 blocks and a whopping 16.384 different permutations. As if the seven block version weren't hard enough, I got the nine block version instead.

By rotating each individual block at a time, the goal is to have a valid equation on all four sides of the snake.

The nine blocks on the snake are held together by a string and have a few particularities: fortunately, each block has a number from 1 to only 4 engraved on it, otherwise the possibilities would been even higher; each block number is alternated by one with the four operations (+ -  ÷  x), and here, operation priority is not a taken into account; also, each block has a different sequence of numbers and operations. For example: by rotating counterclockwise, the first block number has a sequence of "1, 2, 3, 4", but the second has a different one of "1, 3, 2, 4", and so forth... The operation blocks follow this same logic.

I've had this puzzle for more than a month and have been trying to solve it since, although not exhaustively, as I've played with other puzzles as well. Suffice it to say, I haven't been able to solve it yet... The main problem has been to find a good strategy in order to get a more direct solution, instead of resorting to luck alone. Opening a 4-digit vault would be easier...

I believe that there's got to be a way to discard many of the possibilities by some sort of calculation, but I have no idea as to how I can do that. If by any chance, there's a math wiz reading this review, I would really appreciate some pointers. Not the solution, though.

Closing Comments:

For math lovers who like a challenge, the Math Snake is a perfect puzzle. Presentation wise, the design is really clever and the wooden blocks with the engraved numbers are worth taking a try, even if you're not that good at math.

To get a Math Snake, you can visit Puzzle Crafthouse website. One thing worth mentioning is the fact that there are more than 20 different solutions. Not on the same snake, though,but if you want, for example 10 snakes, just contact Puzzle Crafthouse customer service and they will provide you with your 10 different snake challenges. Great for schools or other projects.

The Shipper's Dilemma (or Conway's Packing Box) by mathematician John Horton Conway is no ordinary Assembly Puzzle. The version I have, manufactured by Puzzle Crafthouse is a puzzle solver dream, but it can also turn into a nightmare in just a few hours of failed attempts.

There are 17 pieces and they can be grouped into three categories. Counting the smaller five cubes as a unit area, the other two types are 2x2x3 and 1x2x4 cuboids with six pieces each. Your task is to unpack the pieces and be able to assemble them again into a 5x5x5 cube.

The mathematical relations between the three types of pieces is fascinating. For instance, two 3x2x2 side-by-side pieces standing up, have the same length as a 1x2x4 piece lying down... And there are several more lengths relationships between the pieces. You will notice them as you try to solve and analyze the puzzle yourself.

I have seen this concept before, where you have to assemble a certain number of regular-shaped pieces into a given shape. I have two small puzzles in my collection that fall into this category, but with less pieces (both with 9), thus much easier. See here and here. Since I've solve these two in a relatively short time, I thought that the Shipper's Dilemma, while having more pieces, shouldn't be that hard. How wrong I was...

Usually, I like to solve a puzzle before writing a review for it. Not just as a personal goal, but also to have more insight and understanding of the mechanics involved, behind the puzzle itself. This time, however, that requirement wasn't met and I'm yet to solve it. I have been trying unsuccessfully for more than a week and I've lost count how many different ways the pieces were packed.

An interesting observation by the inventor himself is that the puzzle is almost impossible to solve by randomly assembling the pieces, and I have to agree. The number of pieces involved, which is uncommon for most Assembly Puzzles, makes a random approach pointless, because the possibilities are almost endless. You do have to carefully analyze the puzzle and try to do it in steps, always keeping in mind the very important length relationships between the pieces.

I'm not sure how many solutions are there for this puzzle, but I'm assuming by the nature of the pieces and by the large number of packing combinations, that there are several possible solutions. Finding one might prove to be a tough test to your patience and solving skills. If you know the exact number of solutions, let me know by leaving a message in the post's comments.

EDIT: Thanks to the quick answer by Coaster1235 and contrary to what I previously thought, I know now that the Shipper's Dilemma has indeed 1 unique solution. Proof that this is one devilishly hard puzzle... Feeling challenged enough now?

EDIT 2: Dave Janelle from Puzzle Crafthouse has sent me a presentation with analysis and instructions of the Shipper's Dilemma written by Mike Czerwinski. I gotta say, the analysis is brilliant and it just makes the whole concept seem so simple, that it's used by educators to explain various mathematical principles, such as areas and volumes or size relationships between different cubic shapes. If you're interested in knowing more about this, please contact Dave at Puzzle Crafthouse.

Closing Comments:

Even though I haven't solved it yet, doesn't mean I dislike the puzzle any less. On the contrary. The Shipper's Dilemma is one of the hardest Assembly Puzzles I've tried and I will continue to try it. You are provided with a solution sheet, but I will resist to look at it for as long as I can... Until I give up someday...

Besides the solving part, the presentation of the puzzle is very nice and the quality is flawless. I love the straight lines that criss-cross the entire outer box, which gives it a more elegant look. Oddly enough, I also love this smokey smell of the pieces, particularly coming from inside the cover. Not very commonly "seen" in puzzles, but I still like it.

The Shipper's Dilemma can be found at Puzzle Crafthouse and you can choose between two size models. $13.5 USD for the 0.7lbs version or $16.95 USD for the 1lbs version.

(Click to Enlarge)

Invented by McLoughlin Bros in 1888 and later published in the "New Book of Puzzles" by Jerry Slocum and Jack Botermans in 1992, the Giant Puzzle was then picked up by Creative Crafthouse, who now produces this version. You can see the original puzzle here.

Now with a modern makeover and easier to manipulate, thanks to the handles in each piece, the basics of the Giant Puzzle remains the same.

You're given 25 pieces, 5 of each color and every one of them has a different odd number from 1 to 9, so no two pieces are the same. The puzzle comes in the state as you see it in the above picture and your task is to place the pieces in the tray so that no number or color is repeated in any row, column or any diagonal. You also have to keep in mind that in every row, column and the two major diagonals have to add up to 25, although this is achievable if you get the colors and numbers challenge right, so you don't have to think about that.

The Giant Puzzle is rated as very hard, but I actually found it to be quite easy and simple. The logic is very much similar to what you're used to in a regular Sudoku game, where you use elimination to find a correct placement for a number, in this case a piece. If you're not familiarized with the Sudoku concept, you can try separate challenges first: You can start by getting just the color pieces in the tray, so that they follow the puzzle's rules or if you prefer, start by the numbers instead. Once you have that logic learned, the full task may seem a lot easier then.

(Click to Enlarge)

The next two paragraphs contain spoilers on how to solve the puzzle. If you wish to try it for yourself and prefer not knowing the solution, jump to the "Closing Comments".

Ok, so when you see the puzzle for the first time, you'll notice that every row is the same color and every column has the same number, but if you look closely at the main diagonals, you can see that both of them follow the three basic rules (no repeated color, number and add to 25). Then, you just have to start placing the pieces in the order you saw them in the diagonal, but now in a row or column, which way you prefer.

Assuming you started by a column with the "Yellow 1" piece, followed by the "Red 3" and the "Blank 5" like I did, the next piece you should think about is the "Red 1". You can't place this one at the start of the second column, because you'll repeat the number 1. You can't place it in the second space, because you'll repeat the color red and the diagonal with the "Yellow 1" in the first column. You can't place it in the third space either, because it'll be in the diagonal of the "Red 3". So, by the logic of elimination, it can be placed in the fourth space. Following the same thinking, the next piece has to be the "Blank 3". Since there's six spaces in every row or column and you're now occupying the last two spaces of the second column, the logic continues at the beginning of the same column and down until completed. Repeat the same steps for the remainder of the columns and you'll have the Giant Puzzle solved.

Closing Comments:

Although I found the puzzle to be easier than I was expecting, it doesn't spoil the fun of solving it in any way, and if you're a collector like me, you'll most certainly want to own a high-quality copy of this classic puzzle in your collection.

The Giant Puzzle can be found at PuzzleMaster for $24.99CAD. Here's more puzzles from Creative Crafthouse.

The Brain is a very interesting puzzle, using the Gray Code concept (after Frank Gray) or reflected binary code, which is a binary numeral system. It's produced by the American company Mag-Nif and dates back from 1973. It's still sold today and is actually one their most successful brainteasers to date.

The objective of the puzzle consists of getting all of its eight pegs out, but to achieve that you have to do a sequence of 170 correct moves. Sounds scary, but don't be intimidated by the big number. This may take some time to get used to if you're a casual puzzler, but it becomes quite easy and simple once you understand the logic.

Limiting your movements is a stack of disks that are locked and with every step, you will unlock them one by one until you have all the pegs out. Each peg is numbered from 1 to 8 and they can only have one of two possible positions. When they're closer to the center, they have a value of 0 or In, and when they're outwards, they have a value of 1 or Out. To move a specific peg, you need to make sure that you have the immediate lower numbered peg out and all the remaining lower ones in. This process is exactly the same until you have all the pegs out.

Solving the puzzle will depend on how fast is your understanding of this logic is. It took me about 20 minutes or so to solve it and to get all pegs in again, it took less than 10 minutes, because I had the process all memorized by then. A similar puzzle based on this concept, the Spin Out, actually took me much more time to figure it out. Probably because at the time (three years ago), I was more inexperienced with these type of puzzles...

The current design of The Brain is pretty much the same from the original version, but the color has now been changed from black to red and the transparent plastic has a black and silver glitter effect. I don't have the older version to compare, but from what I've seen in photos, I like the appearance of this one better.

The Brain is a great example on how to turn an otherwise boring mathematical problem, into an interesting challenge and very fun to solve. It's a shame there's not many puzzles out there that use the Gray Code. I, most certainly, would love to try other puzzles like these. Besides this one and the Spin Out, I only have the Chinese Rings and Tower of Hanoi.

The Brain can be purchased at SeriousPuzzles.com.