Sudoku is the addictive number puzzle that has taken the UK by storm and is now taking over the rest of the world. Since it first appeared in The Times in late 2004 its popularity has grow so that it appears in most UK newspapers and has spread to countries from India to Canada, Australia to South Africa.

So what is Sudoku all about? Sudoku is played on a nine by nine grid which is divided into nine smaller squares. The object of the puzzle is to fill in the digits from 1 to 9 so that it appears only once in each column, row and small three by three square. You are given some of the numbers and you have to use logic and deduction to find the position of the other numbers.

Simple? Well, it depends! A Sudoku puzzle can vary from easy to absolutely fiendish. Certainly the more numbers you are given to start off with, the easier the puzzle, but it also depends on which ones the puzzle setter offers. Traditionally there should be no more than 30 numbers given.

Sudoku first appeared in a US puzzle magazine in the late 1970s, but was then picked up by Japanese publisher Nikoli who dubbed it Su Doku or 'Solitary Square' and the puzzle-hungry Japanese loved it. From there it was discovered by The Times and the rest is history.

Sudoku is solved simply by logic; there is no maths required. You may at first be able to fill in a couple of numbers where it appears in every column and row but one. Next you may need to mark up possible candidates in the empty squares until only one possibility remains. Like so many puzzles there will be times when you stare hopelessly and others where the answers jump out at you.

The sudden popularity of Sudoku may be due to many things. It requires just enough brainwork to give a feeling of satisfaction when the puzzle is complete, without taking up huge amounts of time and it requires no special knowledge unlike for instance crosswords, which may require a wide vocabulary.

For hardcore Sudoku fans there are now even more difficult versions. There are sixteen by sixteen square versions which include letters as well as numbers, and a three dimensional version called the Dion Cube.

There are benefits to doing Sudoku puzzles too - the sort of exercise which the brain gets from logic puzzles can help to stop memory decline, make you smarter and even halt the progress of Alzheimer's disease. Teachers are even giving simple versions of the puzzles to pupils to help develop their logic skills. So next time you see one of those nine by nine grids in your newspaper, give it a go. Your brain might just thank you!