Test your powers of logic with 200 number puzzles from The Times Just like a mathematical crossword, these puzzles are ideal for fans of Su Doku who relish grappling with figures. Contains four levels of difficulty, combining arithmetic with an intersecting layout: Mild, Medium, Tricky and Tough. Kakuro originated in the United States in the 1950s under the name of Cross Sums. A logic puzzle, the aim is to complete a grid using digits from 1 to 9, with the digits in each row/column adding up to the clue for that block. It’s similar to Su Doku in the sense that digits cannot be repeated in a row/column.