Sudoku is a logic-based number puzzle that does not involve arithmetic. Although first published in an American puzzle magazine in 1979, Sudoku gained popularity in Japan in 1986 before becoming an international craze in 2005. The goal is to enter a numerical digit from 1 through 9 in each cell of a 9×9 grid, without repeating a number in any row, column, or 3×3 sub-grid. After picking up some on tips at the following sites, you can try your skills at the Surfnetkids Daily Sudoku Puzzle.