Sukaku ("Suuji Kakure"; also known as "Pencilmark Sudoku") has 81 groups of digits in a 9 x 9 grid. Like a standard sudoku, the puzzle must be completed in such a way that each row, each column and each 3 x 3 box contains digits 1 through 9. Only the candidates shown in the grid can be used. mind puzzles for adults - mind puzzle books for adults - mind teasers puzzles for adults - puzzles engage your mind - easy mind puzzles - mind puzzle games for adults - active minds jigsaw puzzles - brain puzzles for adults - brain puzzle books for adults - brain puzzle books - brain teaser puzzles - brain puzzle challenge - brain puzzle games - active minds puzzles