Killer sudoku is similar to the other levels in that each of the numbers 1-9 must fit into each 9-by-9 square. No number can be repeated more than once in the square or in a horizontal or vertical row ...

Life sometimes feels like a puzzle. We tackle the world, moving left, right, forward and backwards just to be able to find ...

Killer sudoku is similar to the other levels in that each of the numbers 1-9 must fit into each 9-by-9 square. No number can ...

Bonus tip: audiobooks also count! Want to upgrade your brain? Learn a second (or third!) language. Studies suggest bilingual ...