Erasable Games Weblog

(Sudoku in words and pictures)

Archive for December, 2007

Crop Circles Sudoku

Monday, December 31st, 2007

Crop Circles Sudoku

So as I was waiting for my Toyota Matrix (dashboard view) to be serviced, I was reading fairly metaphysical Book called 2012, The Return of Quetzalcoatl, by Daniel Pinchbeck. who spends some time discussing people who take crop circles seriously. Note the cover art.

It occurred to me that because there have been so many instances of crop circle manifestations, especially in the United Kingdom, that the sheer precision and incuse designs would provide clear examples of geometric one-to-one correspondences with the first 9 digits. Clearly, if aliens are trying to communicate with humanity, using geometric art as the communication medium offers a common reality that beats the symbols we use for our number system(s).

I am indebted to Lucy Pringle’s Crop Circle Photographic Library for these images. Her collection of photographs of these mysterious, aerial views of crops bent artistically is extraordinary.

She is a leading researcher and author of 3 books on the subject — Crop Circles: Greatest Mystery of Modern Times (2000), Crop Circles (2004), and her latest Crop Circles: Art in the Landscape (2007).

I hope this cartoon helps to publicize her efforts to bring serious attention to all humanity (who’s interested) in this curiously ignored, yet significant messaging system between an unknown entity or entities and humanity.

I wish a happy new year to all, worldwide. Whenever you’re ready.

Akari (Light Up) On Sudoku

Sunday, December 23rd, 2007

Akari (Light Up) On Sudoku

In the Western World, December is often host to festivals of Light. I’ve adapted a puzzle called Akari or Light Up which was originally invented by Nikoli in 2001. His site provides a tutorial for how the rules of the game interplay. Sample puzzles may be found on Nikoli’s Website, which vary in size from 10 x 10 to 36 x 20.

The puzzle shown in the cartoon is fairly easy to solve. It’s a little reminiscent of the old computer game called Minesweeper. Minesweeper offered adjacency clues which included the boxes diagonal to as well as number of exposed sides. When you incorrectly clear a space that was a mine, a rather startling bang! terminates your game. No sound effects for Akari, however.

The Wikipedia article for Minesweeper has a fascinating discussion about patterns and solving strategies by analyses of single and multiple boxes and mine probabilities. Board difficulty measurements are also detailed.

Some online sources of puzzles include: (online player, pdf puzzle generator), 100 Free Akari Downloadable Puzzles at (zipped pdf files), and for online games of varying difficulty.

Have a most enjoyable holiday! I’m glad to enlighten you or at least lighten your mood.

Do-Sum-Oh (Squiggly) Sudoku

Sunday, December 16th, 2007

Do-Sum-Oh (Squiggy) Sudoku

I came upon Squiggly Sudoku puzzles at Bob Harris’ site. This variant emphasizes the distortion of the 3×3 squares into irregular geometric shapes also containing 9 squares each. His site contains a proof that n-1 starting numbers (or letters) Du-Sum-Oh (Squiggly) exists uniquely for any n x n sized puzzle. The puzzle above has n starting letters for a 9 x 9 sized puzzle, so it should be easier.

Bob Harris offers various sized puzzles on his website and has published a book called Squiggly Sudoku (Sudoku With A Twist) containing 120 various sized puzzles.

He also provides a useful tutorial about how to solve these puzzles. He cites the Big (and Little) Law of Leftovers. The Big Law of Leftovers: Wherever a group of regions overlaps some rows or columns, the parts outside the overlap (the leftovers) have to be the same.

Another pair of authors, Gideon Greenspan and Rachel Lee provide another book of 200 puzzles, also called Squiggly Sudoku However, of these 200, only 144 are Squiggly Sudoku puzzles, the rest are either classic Sudoku (40) or Samarai Sudoku (16) of various levels of difficulty. They also maintain a Website called Web Sudoku with daily (printable) squiggle and other puzzles.

Another Web Site that provide Squiggly Sudokus is Daily Sudoku By Sam Griffiths-Jones. He is also responsible for several sudoku books, including one for kids and an advanced puzzle book. He also sells Electronic Books of puzzles including Squiggly Sudoku puzzles.

This cartoon is comparable to the cartoon I published last June 2, 2007, called Jigsaw Sudoku where numbers instead of letters were used.

While Sudoku puzzle solving is a great boon to maintaining/increasing cognitive brain function, some may eventually get bored with it, hence the invention of Sudoku variants. The fact that boredom sets in to a previously stimulating activity is just human nature. Similarly doing the same physical exercise initially builds muscle tissue but after a while it no longer does.

There is an indication (See Carved in Sand: When Attention Fails and Memory Fades in Midlife by Cathryn Jakobson Ramin, for example) that our brains, when exposed to greater stimulation have a greater number of healthy nerve cells and stronger connections between them. The act of doing puzzles for example, requires continuing novelty to provide sustained stimulation (and interest). The practical consequence of this is to keep our brains agile throughout our entire lives and not have it turn to oatmeal before we’re ready.

Playing Card Sudoku

Sunday, December 9th, 2007

Playing Card Sudoku

Today I am applying the most popular and historically enduring card games using its playing cards to Sudoku. Card Games have been manual endeavors but have tapered off after the 1990s when PCs became sufficiently prevalent. Only since the advent of PCs has digital computer software been written to simulate card games, notably one player Solitaire based games which were a strong motivator of and user interface training, once the PC was available (in offices and homes!).

They are now supplanting physical card games, perhaps most due to the “(double) click” that properly places a card where it should go. This is infinitely more convenient and immeasurably speeds up the game compared with picking up a card and putting it where it belongs. I’m sure some people may “click” on principle just in case the software knows more than they can see (at 3AM).

My favorite visual humor involving Solitaire for the 80s and 90s is shown here.

One way to merge (really small) playing cards with a Sudoku board is to use velcro on all the cards and in each square. Your Sudoku (partial) solutions will persist much longer.

Some interesting Card Game sites include The House of Cards which has information and rules for many kinds of games involving playing cards as well as downloadable software and online versions of card games.

The Card Games Web Site has card and tile games from the world over as well as many links to other card game and card related sites.

Of course, Hoyle’s Games, Improved And Enlarged is a mainstay for Card game rules and mathematical analysis (of odds) since 1835.

Since card games have been around since before 1000 A.D., Where they are believed to have originated in Central Asia and spread to the Moslems and then to Europe and finally to the North and South America and Australia. Look at A Brief History Of Playing Cards” for many fascinating details about the playing card evolution, especially after 1800 in the United States.

The following site also has historical but not necessarily currently played card games:
Rules To Period Games

Thanks to all who are following my whimsical Cartoons involving Sudoku variants.

Slitherlink On Sudoku

Sunday, December 2nd, 2007

Slitherlink On Sudoku

A big thanks to Jim Bumgardner ( for motivating this Cartoon about Slitherlink puzzles. I had not played this before, but it is quite absorbing. His site provides many sets (books) of 16 Slitherlink puzzles in PDF format, along with their unique solution. They are organized according to level of difficulty. In every even numbered book set, the number counts in each puzzle are symmetrically placed, but the solution is definitely always asymmetrical.

In his instructions, he suggests that dot connections that cannot logically occur should be indicated by a thin x so that the remaining possibilities stand out. In the puzzle above, there would be an x between the 3 and the 0, enabling the 3 to be fenced as shown.

Slitherlink is also known as Takegaki along with other names in Wikipedia. The site also provides solution strategies. Another site that has interesting tutorial is the Nikoli puzzle site. Slow motion animated practice always trumps verbal description. has an FAQ that is very helpful in visualizing what can and cannot be drawn. Puzzles there range from sizes 5×5 to 25×30 in difficulty levels Normal and Hard.

Hirofumi Fujiwara has provided an excellent (non-obvious) “Key to Solution” set of basic, general and strategic rule sets. His site Puzzles And Java World also has puzzles online written in Java including Sudoku, Paint by Numbers, Cross Sums, and Sliding Piece Puzzles.

So don’t sit on the fence! Extend it!