Have you heard of KenKen? It is a style of arithmetic and logic puzzle similar to Sudoku invented in 2004 by Japanese math teacher Tetsuya Miyamoto who intended the puzzles to be an instruction-free method of training the brain. The name derives from the Japanese word for cleverness! As in Sudoku the goal of each puzzle is to fill a grid with digits –– 1 through 4 for a 4×4 grid, 1 through 5 for a 5×5, 1 through 6 for a 6×6, etc. –– so that no digit appears more than once in any row or any column.Grids range in size from 3×3 to 9×9.
Additionally, KenKen grids are divided into heavily outlined groups of cells –– often called “cages” –– and the numbers in the cells of each cage must produce a certain “target” number when combined using a specified mathematical operation (one of addition, subtraction, multiplication or division). For example, a linear three-cell cage specifying addition and a target number of 6 in a 4×4 puzzle must be satisfied with the digits 1, 2, and 3. Digits may be repeated within a cage, as long as they are not in the same row or column. No operation is relevant for a single-cell cage: placing the “target” in the cell is the only possibility (thus being a “free space”). The target number and operation appear in the upper left-hand corner of the cage. (Wikipedia)
Here is a short instructional video on how to play KenKen: https://www.youtube.com/watch?v=q2Un71kE2Xs
A video in German describing what KenKen is and how to play: https://www.youtube.com/watch?v=sJTVsXe5NeQ
And link to puzzles of varying levels here: http://www.kenkenpuzzle.com
There is a cool new movie about the creator and people who are fascinated by the puzzles called “Miyamoto and the Machine.” Not sure where you can see it at this time, but you can view the trailer here: https://www.miyamotoandthemachine.com