About two years ago, when I wrote my first article on numerical puzzles here at Blogcritics, I mentioned that a myriad of numerical puzzles have come up since the breakthrough of Sudoku. Since then, even more different variants are puzzling the minds of devoted solvers.
Surely the most prominent variation are CalcuDoku puzzles, which first appeared in 2008. They are originally known under the name KenKen , but since this word has been trademarked by Nextoy, LLC, the rest of the world had to come up with a different one.
Leaving the naming issues aside, lets go back to the puzzles themselves. They share some common rules with Sudoku and in fact, very much resemble Killer Sudoku. Your goal is still to fill in the grid without repeating any numbers in rows and columns, however there aren't any 3x3 boxes as in classic Sudoku. In fact, the puzzles need not necessarily be 9x9 in size - they range from 4x4 to 9x9.
Similarly to Killer Sudoku, the grid is not populated with any "givens"; instead, groups of cells are enclosed in "cages" with a number and one of the four basic arithmetic operators (addition, multiplication, division and subtraction). You must solve each cage so that the numbers in it result in the total given for that cage using the appropriate arithmetic operation. It sounds complicated, but it's much easier when you look at this sample puzzle.
So, for example, since we are working on a 6x6 grid (using only the numbers 1 to 6) the cages consisting of two cells, with "4-" as the clue, could only be either "6-2" or "5-1". Get it? Okay, this doesn't solve any cells, but it limits the candidate numbers for some cells.
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