There is the board which attracted 81 piece of the 9x9 unit to the screen. There is the group which attracted piece of 3x3 in the board (surrounded in bold line). There is empty piece to the board and can put numbers from 1 to 9. Become game cleared if you put the number of the correct answer in all pieces. But each piece is different in the number of the correct answer every question. Group of the piece and vertical, horizontal piece do not contain the same number (the applicable range yellows). In other words the number that each piece contains is one by all means. Each empty piece can make a memo to six numbers. Use this memo well and arrive at the number of the correct answer.