Ace Sudoku

Ace Sudoku is a puzzle game. Free. It is easy to learn but a challenge to master, puzzling players all over world. There is really only one rule to Sudoku: Fill in the board so that the numbers 1 through 9 occur exactly once in each row, column, and 3x3 box. Your initial game board will consist of several numbers that are already placed. Those numbers cannot be changed.