Japanese math teacher Tetsuya Miyamoto created the first KenKen puzzle in 2004.

KenKen puzzles are often compared to sudoku puzzles.

<i>Ken</i> means wisdom in Japanese, so "KenKen" roughly translates to wisdom squared.

Basic arithmetic skills are needed to solve KenKen puzzles.

The computer program that creates today's KenKen puzzles is called the Kenerator.

The Times (UK) first began publishing KenKen puzzles daily in March 2008.

Nextoy, LLC began marketing the puzzle worldwide in 2008.

In 2009, Reader's Digest became the first U.S. magazine to publish a KenKen puzzle.

Will Shortz has been the editor of The New York Times' crossword puzzle since 1993.

KenKen puzzle grids must be at least 3-by-3 and no larger than 9-by-9.

The outlined boxes within each KenKen grid are called cages.

Each cage might specify the use of addition, subtraction, multiplication or division.

Numbers cannot be repeated in any row or column.

Each puzzle has only one correct answer.

Numbers one, two, three and four are used to solve a 4-by-4 puzzle.

Miyamoto's school accepts only the first 20 students who apply.

Miyamoto does not give any formal instruction to his students; he believes people learn better by solving puzzles on their own, thus exercising their brains.

There are six new puzzles of varying difficulty each day on KenKen.com.

In general, larger-grid puzzles are harder than smaller-grid puzzles, but that's not always the case.

Cages with even numbers of boxes aren't necessarily easier to solve than cages with an odd number of boxes.