Polydron Sudoku14 February 2017 | Paul Stephenson Most Sudoku puzzles use the numbers 1 to 9, but you can use anything – letters, colours, shapes, …And you can make up puzzles with fewer items. We shall use just 4. If you think such puzzles are likely to be too simple, I warn you that we shall move from 'single' Sudoku to 'double' Sudoku and even 'triple double' Sudoku. To continue reading please click here to view and download the PDF. | 