You are powerless to stop KenKen. Perhaps the new Japanese arithmo-logical challenge, which debuted in the New York Times on Feb. 8, will burrow into your brain on account of a significant other, who will plead for your help as she softly coos the game's tantalizingly simple rules. Or maybe a boring subway ride will leave you staring at a discarded newspaper, from which an unsolved KenKen will silently beckon your understimulated brain. However it goes down, don't try to resist. The marketing wheels, greased by the promise of Sudoku-style riches, are already in motion. New York Times puzzle maven Will Shortz calls it "the most addictive puzzle since Sudoku." He'd better hope so, as Shortz has already put out a slew of books of this computer-generated brain-mangler, with titles like Will Shortz Presents KenKen Easy to Hard Volume 3, Will Shortz Presents: I Can KenKen! Volume 1, and Will Shortz Presents the Little Gift Book of KenKen.
What exactly is this new creature? Like Sudoku, KenKen is a simple game whose rules can be expressed in a couple of bullet points:
- Fill the grid with digits so that no digit is repeated in a row or column. In a 4-by-4 grid, you'll need to use the digits 1, 2, 3, and 4 in each row and column. In a 5-by-5 grid, you'll use 1, 2, 3, 4, and 5—and so on as the size of the grid increases.
- Within each outlined set of boxes—these sets are called "cages"—use the given arithmetical operation to arrive at the number indicated.
Here's a sample grid:
Take a look at the two-box cage in the upper-right of the diagram. Your goal is to place two digits in this cage such that the difference between them is 1. You can subtract either backward or forward—if you want to use the digits 1 and 2, it's valid to put the 2 to the left of the 1 or the 1 to the left of the 2. In the three-box cage below it, you need to multiply three digits to get 60. Since this is a 5-by-5 puzzle, there is only one potential combination that will work: 5, 4, and 3. It's up to you to figure out what order the digits need to go in for the puzzle to be solved correctly. (To see the solution, click here.)
KenKen—tip for wannabe puzzle-craze instigators: the name was cleverly trademarked by its promoters to discourage too-blatant imitators—does share some features with Sudoku. Both demand high-powered deductive reasoning skills from solvers, for example. The big difference between the two is that Sudoku has nothing to do with math—you can play with symbols rather than numbers—while KenKen requires some degree of arithmetic skill, especially with larger puzzles. If you're solving a 9-by-9 grid, you may be required to multiply, say, 7 by 5 by 9 by 3 in your head. If the KenKen people are smart, they'll market a branded set of calculators for the mathematically impaired.
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