Sudoku, despite the Japanese name (which means 'single number'), was invented in America by Indiana man Howard Garns. Garns was a 74 year old retired architect, and made puzzles as a hobby. The first Sudoku games were published in 1979 by Dell Magazines and called Number Place. It was introduced in Japan in 1984.

In 1997 Hong Kong judge Wayne Gould saw a partly completed puzzle in a Japanese bookstore and subsequently wrote a computer program to make unique puzzles automatically. After this, The Times in Britain started publishing the puzzle. It subsequently went on to garner incredible popularity in both the UK and United States.

The rules of sudoku are quite simple. Every row, column, and 3 by 3 square must contain every digit 1 to 9.

If you wish to add notes, simply press shift along with the number you want to add.