Hot on the heels of Sudoku comes Kakuro. Think of them as the mathematical equivalent of crosswords. Also known as Cross Sums or Kakro in Japan they have recently come to the UK featuring in The Guardian newspaper. A Kakuro consists of a playing area of filled and empty cells similar to a crossword puzzle. Some black cells contain a diagonal slash from top left to bottom right with numbers in them, called ?the clues?. A number in the top right corner relates to an ?across? clue and one in the bottom left a ?down? clue. The object of a Kakuro is to insert digits from 1-9 into the white cells to total the clue associated with it. However no digit can be duplicated in an entry. For example the total 6 you could have 1 & 5, 2 & 4 but not 3 & 3. Sound simple? Be warned it gets hard and is as addictive as Sudoku.