Hailed as the 21st Century's Rubik's Cube the puzzle was originally created by Swiss mathematician Leonhard Euler in 1783 as a mathematical illustration of a concept, which I can't remember.

It was adopted by the Japanese as an alternative to Crosswords - as it is difficult, if not impossible, to create a crossword for ideograms! The puzzle came to prominence after a Tokyo-based publisher spotted a "Magical Square" puzzle in an American publication. The Japanese renamed it Su Doku, which, apparently, means "Solitary Number", and so a phenomenon is born.

This phenomenon hit the UK back at the end of 2004 thanks to the Times newspaper - which has been publishing them ever since - and spread to virtually every other daily newspaper after a few months... (although it had been around on the UK puzzle scene since the early '80s - probably called Magical square...)

Various variations have arisen over this period - including the Times Samurai Sudoku and the Telegraphs Dion CUBE Sudoku...

The basic premise is very simple - there is a grid of 81 squares which needs to be filled in with the numbers 1 to 9... The only restriction is:

No Logical unit can contain duplicates of the same number

There are usually 3 types of Logical Units
1) Rows
2) Columns
3) "Cells" (a Cell is a group of 9 squares - usually, although not always, the 81 squares are split up into 9 3x3 "Cells").

I have also seen variations on the total number of squares and the number of squares per logical unit... Favourites seems to be: 6, 8 and 10 and 16 (and now 42!!!).

A "pure" variant should - imho - be considered as only for "square" numbers - i.e. 4,9,16,25,36,etc...

There are various websites out there with Sudoku puzzles on them - some to be completed online, some to be printed and completed offline two of my favourites (one of each) are: http://www.mousebreaker.com/games/sudoku/play.php and http://www.dailysudoku.co.uk/sudoku/index.shtml

There are also various Sudoku solvers - which rather misses the point, methinks (so I won't include any links to them)...

I'll post a puzzle on a separate page, with the intention to change it once a week===>

Here's the first one: A5185280
Second H2G2 SuDoKu: A5255318
And here is the insane SuDoK42 - 42 Cells, 42 Columns, 42 Rows...: A5250601
Second (slightly less insane) Puzzle here: A5475431