Puzzle book
Cross sums, from easy to impossible
Each grey square says what the row to its right and the column below it have to add up to. You write the digits 1 to 9 in the white squares, and no digit repeats within a series.
Five levels, and the grid grows with the level: 9×9, 11×11, 13×13, 15×15, 17×17. At the back, a table of every sum that allows only one combination.
Each white run adds up to the number in the triangle in front of it, and no digit repeats inside a run.
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.
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