To fill an idle moment, there's nothing I like more than a quick go at a suuji wa dokushin ni kagiru.  Which incidentally means 'the digits must remain single'.

My first foray into the world of Suduko began on 7 July 2005.  I very rarely have a newspaper, but had decided to purchase a copy of The Times, being the London Olympics celebration edition.

As I sat that evening, with the endless coverage of the London bombings being relayed on the TV, I turned to the back of the paper and started to become hopelessly addicted to the number puzzle.

Now, I read, about 140 newspapers worldwide feature Suduko puzzles and there are 328 books available on Amazon to buy.

After a long Summer holiday, feverishly completing grids printed from the internet and newspaper supplements, I began to tire of the standard 9x9 grid.  My preferred puzzle now is the Killer (seen above) - in which normal Suduko rules apply, but a dotted line indicates the total for the numbers contained within it.  I have just finished the Times Killer Suduko book and am eagerly awaiting Edition 2 to become available.

Two mathematicians have calculated that there are 6,670,903,752,021,072,936,960 different valid Suduko grids, which should mean that we won't run out of puzzles until some time early in the 3,607,744th century.

I'd better go and sharpen my pencil again...