ALL the most entertaining pencil-and-paper puzzles come from Japan. Sudoku is the best known, but there are hundreds more. I鈥檝e selected two types of puzzle from my recent book that I think 快猫短视频 readers will particularly enjoy. In each, the grids can be filled in through logical deduction alone.
KenKen
In 2004, maths teacher Tetsuya Miyamoto wanted to create a puzzle for his classes of 8-year-olds using the basic arithmetical operations: addition, subtraction, multiplication and division.
So he devised KenKen, which became a hit in Japan and now features in some UK newspapers. However, in the newspaper version, the mathematical symbols for the arithmetical operations required are always written in the grid. Too easy!
In the two examples here (top left and right), which Miyamoto designed by hand, the symbols are omitted, making for a much more interesting challenge. The number of ninja heads indicates the level of difficulty.
The rules: fill the grid with the numbers between 1 and the total number of rows (1, 2, 3, 4 in a 4脳4 grid, for example), so each number appears only once in every row or column. The grid is divided into 鈥渃ages鈥�, each containing a target number in its top left corner.
Using only one arithmetical operation in each cage, either +, 鈥�, 脳, or 梅, you must produce the target number using all the numbers in that cage. So, if there are two cells in a cage, the numbers in those cells must either add, subtract, multiply or divide to make the target number.
Straight Cross
What would you get if you combined a crossword with a sudoku? Puzzle creator Naoki Inaba set himself this challenge and came up with Straight Cross. I find it more rewarding than sudoku, since you must take into account the numerical value of the number, which adds an unusual twist. Try these two examples (bottom left and right).
The rules: fill the cells with numbers from 1 to 9 (but not necessarily all of them) so each horizontal and vertical strip contains consecutive numbers. A strip is made up of adjacent white cells between the edges of the grid and/or black squares. Although the numbers must be consecutive, the sequence needn鈥檛 start with 1 and the numbers can be in any order. So, if the digits are 2, 3 and 4, for example, they could be in the order 2-3-4, 2-4-3, 3-2-4, 3-4-2, 4-2-3 or 4-3-2.
For solutions, see Test yourself against these superpuzzles from Japan: Solutions
(Guardian Faber)
This article appeared in print under the headline 鈥淭hinking inside the box鈥�