If you are a Sudoku fanatic and have an iPhone, there is a website just for you: http://www.enjoysudoku.com.

This site offers the most intuitive interface for Sudoku since the pencil. There are new puzzles every day and they are offered at seven levels of difficulty ranging from Beginner to Fiendish. Even the ‘Moderate’ setting offers a challenging puzzle and they go up from there. One nice feature is that once you select a number to work on, the game highlights all of those already on the board. If you make a mistake by placing a number on a line already occupied it displays the number in red, so you don’t fat-finger your way into a wrecked puzzle. When you finish a puzzle the system tells you what percentage your time ranks among all the others who have played!