One of my original sudoku creations called "Multiplication Equation Sudoku" was published in the August issue of NRICH.

Please refer to http://nrich.maths.org/public/viewer.php?rss=1&obj_id=6224&part=index

The following variants are representative of my sudoku creations:

1. Ratio Sudoku
in the March 2006 issue of http://nrich.maths.org/public/viewer.php?obj_id=4827

2. Pole Star Sudoku
a difference sudoku variant in the September 2006 issue of http://nrich.maths.org/public/viewer.php?obj_id=5433

3. Quadruple Clue Sudoku
in the September 2008 issue of http://nrich.maths.org/public/viewer.php?obj_id=6225

This variant was used in the 2007 Second World Sudoku Championship, the 2007 Italian National Sudoku Championship and the 2008 Czech National Sudoku Championship.

4. Twin Corresponding Sudoku
in the November 2006 issue of http://nrich.maths.org/public/viewer.php?obj_id=5477

This variant was used in the 2007 Second World Sudoku Championship and the 2008 Czech National Sudoku Championship.

Please note that the variant would remain the same whether it is given the name of "Corresponding Sudoku Twins" or any other label.

My sudoku creation for the October 2008 edition of NRICH in http://nrich.maths.org/public/viewer.php?rss=1&obj_id=6310&part=index is the Addition Equation Sudoku.

My sudoku creation for this month (November 2008) in http://nrich.maths.org/public/viewer.php?rss=1&obj_id=6311&part=index is called the "LCM Sudoku".

For the first time, NRICH uses the creative and innovative idea of flash interactivity for its puzzles.

My first version of "LCM Sudoku" in an earlier issue of NRICH in the link http://nrich.maths.org/public/viewer.php?obj_id=6018 used unknown variables and numbers.

To be more specific, that variant should be called "Algebraic LCM Sudoku".

A more challenging version of the LCM Sudoku has been posted this month (November 2008) on the site http://www.chinasudoku.com/

My sudoku creation for the December 2008 http://nrich.maths.org/public/viewer.php?obj_id=6368 is named "Bochap Sudoku" which combines all four arithmetic operations to obtain the solution.

Happy New Year, everybody!

My creation for this month (January 2009) is "Colour Islands Sudoku" in http://nrich.maths.org/public/viewer.php?obj_id=6405

The variant is based on part of the rules of my two board games.

Back in 2006, only a few sudoku variants such as the Killer Sudoku and Skyscraper Sudoku had been invented.

I can consider myself as the pioneer in the invention of sudoku variants outside Japan. After creating sudoku variants for NRICH and other websites for 3 years, it is time now to look back at what I have invented and achieved since 2006.

My first LCM Sudoku variant was invented in April 2008 as shown in http://nrich.maths.org/public/viewer.php?obj_id=6018

A more difficult version of LCM Sudoku was invented in November 2008 as shown in http://www.chinasudoku.com/

A popular sudoku variant invented by me in November 2006 is the Twin Corresponding Sudoku as shown in http://nrich.maths.org/public/viewer.php?obj_id=5477

I also designed it for the Second World Sudoku Championship 2007 at Prague.

One of my friends just pointed out that he found a so-called "Substitution Twin Sudoku" on one website. The puzzle is similar in every way to my "Twin Corresponding Sudoku" except for its name and its position in a vertical direction. This "new" puzzle was published in 2008 while my puzzle was invented and first published in 2006.

I have to thank that person for liking my "Twin Corresponding Sudoku" so much that he changed its name entirely. It won't be surprising that in the future I shall find other "fans" of mine playing similar jokes on me by pubishing my "Twin Corresponding Sudoku" under other names such as "Replacment Twin Sudoku", "Twin Replacement Sudoku", "Similar Twin Sudoku", "Twin Substitution Sudoku", etc.

With my friends and even some strangers, I have discussed the problem of my sudoku variants popping up here and there like mushrooms on some websites, in books and some international championships. Among them, the opinion of one person, who has a deep interest in Zen, is particularly interesting.

I almost fell off from my chair when he said that such happening shows that my sudoku variants are a great success and it should be viewed as a positive development. He said that my task is to make it "more positive" by thanking whoever is interested in my sudoku concepts and encouraging him to use more of my ideas, whether on websites or in books! He said that I cannot force others to advertise for me, but others cannot stop me from advertising myself . He said I can never stop others from using my ideas, and similarly others can never stop me from trying to get the maximum benefit out of the whole situation.

Now I am putting the advice of that "Zen master" into practice to see how successful it works.

First I have to thank http://www.sudokumasters.in for using my idea of "Twin Corresponding Sudoku" in its so-called "Substitution Twin Sudoku".

I also have to thank http://wsc2008.com for designing a so-called "Group Sum" which is identical to my "Corner Squad Sudoku" in http://www.ageofpuzzles.com/Collections/CornerSquadSudoku/CornerSquadSudoku.htm except that the small clue-numbers in the "new" puzzle are circled.

An article in http://www.notelay.com/articles/did_you_know/what_is_sudoku/ has this interesting comment about sudoku: "Because Sudoku is logic-based, other puzzles could be created that use the same concept and replace the numbers with other objects, such as colours, letters or shapes."

I have used graphics, Chinese words and the alphabet for my Twin Corresponding Sudoku. Please refer to the following websites:

http://nrich.maths.org/public/viewer.php?obj_id=5518

http://www.ageofpuzzles.com/Collections/TwinSudokus/TwinSudokus.htm

http://www.chinasudoku.com/

I have to thank http://wsc2008.com for designing its so-called "Alphabet Substitution Twins". Whatever name the "new" puzzle is called, it is still identical to my "Twin Corresponding Sudoku".

Finally, I hope more people will use my sudoku ideas freely on their websites and in their books, but at the same time as the Chinese saying goes, "remember the source whenever you drink water", so please don't keep me totally out of your limelight.