The challenge comes from having to fill a 9x9 grid so that every row, column and 3x3 box within the grid contains the digits 1-9. Sudoku is a highly addictive blend of logic and lateral thinking. Sound easy? You’ll change your tune after your first round of Sudoku! The rules of Sudoku are simple. The numbers have no numerical or arithmetic value; they represent symbols that cannot be repeated. Enter digits from 1 to 9 into the blank spaces of the board. Every row, column and 3x3 subsection of the grid must contain one and only one of each digit. Each Sudoku puzzle has a unique solution that can be reached logically. There are four levels of difficulty, based on how many numbers are provided when you start the puzzle. EASY: 34-36 MEDIUM: 30-32 HARD: 27-29 GENIUS: 24-26 You can play 50 puzzles per level. Select Statistics to see how many per level you have completed and your best and average time. Source: The Developer Website.