Puzzle book
Five levels of difficulty, from easy to impossible
Two hundred sudoku in five levels that really do climb, one impossible with the fewest clues, and to close, a grid of sixteen by sixteen.
Every grid was generated and checked by computer: each has exactly one solution and can be finished by reasoning alone. You never have to guess.
Fill the 9×9 grid with the numbers 1 to 9, so that every row, every column and every 3×3 box contains all of them exactly once.
Paperback, 8.5 × 11 inches, white paper and big grids. The answers are at the back, at no extra cost. Every puzzle goes through a program that looks for a second solution before it is printed: if it finds one, the puzzle is thrown away.
There is a new Catku every day on this site, free and with no sign-up, and a sudoku, a killer, a kakuro, a 16×16 and a nonogram to play or print.
Play today's
