Erasable Games Weblog

(Sudoku in words and pictures)

Archive for February, 2007

Double Sudoku

Sunday, February 25th, 2007

Double Sudoku
I’m sure some Gemini people (or twins or couples or…) would delight in such puzzles.

Flickr Sudoku

Saturday, February 24th, 2007

A visually interesting mashup of Sudoku and Flickr involving pictures of numbers is shown in Flickr Sudoku. This is an online playable game, (although rendering for the Safari 1.3.2 browser is flawed at the bottom).

Unfortunately, the presentation reminds me of a numerical ransom note. This is not to minimize the great work that went into creating this site. I also like the various (random) Sudoku keyword searches on Google shown at the top. There’s a Time of Day Site called Human Clock that has found and created objects/photos with the correct hour and minute that uses a similar idea.

A more abstract version of the same concept is shown on Becky’s Web where 9 thematically grouped pictures and a blank picture are shown in a playable grid. Like the large varieties of layouts in Mah Jong Solitaire Software Puzzles, the original chinese characters are transformed into various alternative symbol sets.

I believe it is a good idea, when exercising the brain, to expose it to a variety of “settings” or contexts in which puzzle solving logic can be applied. The brain embraces the novelty and adapts to a more flexible solving environment.

Thanks to Webmaster for letting me know about these sites.

Sudoku Or Seppuku?

Sunday, February 18th, 2007

Sudoku Or Seppuku?

For more amplification on this, see Alien Barbeque.

Sudoku Coloring Puzzle

Saturday, February 17th, 2007

Ivars Peterson, written about last week here, has announced his departure from Science News and Math Trek Blog for a position as Director of Publications for Journals and Communications at the Mathematical Association of America (MAA). His new blog, due in March 2007, will be called: The Mathematical Tourist.

Within the MAA Online website, Ed Pegg, back in September 2005, surveyed the varieties of Sudoku and showed many actual variants, some of which are regularly published (especially in Japan). It is an excellent article and a testament to Sudoku puzzlers’ low tolerance for boredom.

I especially like the Cubic Sudoku, which contains 2×4 rectangles on the cube faces with 1×8 “bent in the middle” strips that comprise the “rows” and “columns”. I’m an easy mark for 3-D puzzles.

On a Dutch Web site called Sudokube that I roughly translated with the help of babelfish, there is a hybrid of Sudoku and Rubik’s Cube available for sale for only 7.49 Euros per. (It offers a reduction in price to 5 Euros on its home page.)

This is what I find ironic: the original Rubik’s Cube consisted of 6 colors that get ultimately arranged to have one color per face of the cube. Sudokube has produced a rubik’s-like cube with the digits 1 through 9, in order, on each face, when solved.

Whereas, in my Sudoku Coloring Boards Cartoon of February 10, 2007, I rendered a Sudoku puzzle into a color mapping and a pattern mapping of the digits 1 through 9 from the original starting numbers. I’ve not seen any instances of this variant anywhere else.

I believe this will be very attractive to people whose visual color sense is advanced and whose number sense has been stifled in early life or atrophied. Since I teach math and feel rather un-visual, does anyone else concur (or not) with this?

How do you go about solving the Sudoku Coloring Puzzle as shown in the Cartoon? It seems to me that using small colored dots to make temporary notes in the boxes is analogous to the small numbers one writes as permissible entries. Do you solve the puzzle quicker or slower than one with numbers?

Obviously, solving this is perfect for the Power SudokuČ white board and colored markers found elsewhere on If you lack 9 different solid color markers, you can assign patterns for the missing solid colors instead, although that makes small notes harder to write.

The Puzzle is reproduced here and downloadable as a pdf file:

Sudoku Coloring Puzzle 1 450px

Sudoku Coloring Boards

Saturday, February 10th, 2007

Sudoku Colors 450px
This Cartoon was prompted by the Four Color Problem In Topology and the Color Sudoku book cover cited in the previous post.

MathTrek And Brainfreeze

Saturday, February 10th, 2007

I’ve been subscribing to Science News since 1995. [As I get older, Science (and Religion) become more fascinating.] It’s an excellent weekly news magazine of science, usually about 16 pages with minimal ads and concise (1-2 page), up to date articles. One of the features of Science News is an occasional column (blog) written by Ivars Peterson, called Math Trek Blog.

Mr. Peterson has written several articles about Sudoku for the magazine, notably:
Sudoku Math (June 2005),
First World Sudoku Championsip (March 10-11, 2006),
Pentomino Sudoku (May 2006) and
Sudoku Class (February 2007).

His articles focus on aspects of Sudoku in a clear, concise way and unlike other (opinion) columns, provide a bibliography to other sources of information. His latest, entitled Sudoku Class, provides information about Sudoku in classrooms, Math conferences and describes a Website by Dr. Laura Taalman (of James Madison University) called Brainfreeze Puzzles.

Although not updated in 10 months, Dr. Taalman’s site describes eleven Sudoku variants with examples. She is co-authoring (with Philip Riley) a new book called: Color Sudoku to be published in May 2007, containing examples of these variants. (Perhaps that is the reason for the frozenness [no pun intended] of her website.)

On her University website, Dr. Taalman conducted and preserved a Sudoku Puzzle Problem of the Week contest from January through April 2006. Thirteen downloadable Sudoku variant puzzles (with solutions also available) are shown there. I haven’t tried them yet but plan to.

Fractal Sudoku

Saturday, February 3rd, 2007

Fractal Sudoku
As promised, another conceptual cartoon. I think of the stick-figure as “Cubic” and also “Cubehead”. I’ve always been fascinated by Fractals. A Science Fantasy story by Piers Anthony, called Fractal Mode gives a very accessible discussion of the experience of fractal worlds.

Solving Sudoku Video Animation

Saturday, February 3rd, 2007

There’s an impressive video animation of a Sudoku puzzle (3 MB, 2:26) along with a soundtrack for which I could only hear the first two notes.

It starts and solves a puzzle step by step on Mark Huckvale’s Web site. He is a professor of Phonetics and Linguistics at University College London (United Kingdom).

The video starts with the given starting numbers and the next scene has all the possible numbers in the blank cells except for those used in the same row, column or block. As new numbers are inserted, the remaining unchosen candidates disappear. (A whole lot of erasin’ going on!)

Perhaps it would better mirror the solving reality, if the constraints of the digit being anywhere else but there, were highlighted also (and perhaps spoken). Nevertheless, it is an excellent and insightful example of solving a Sudoku puzzle in under 3 minutes.