A Sudoku a day keeps insanity at bay. That, as my old grandmother used to put it, was derived from an ancient Confucian proverb about the importance of keeping an active mind. For, like the best well-oiled machine, one's grey matter needs regular exercise and plenty of maintenance to keep it tikkety-boo. But for those of you who relish a new and possibly more challenging challenge, we bring you Kenken. No this is not a double-visioned edition of Barbie's significant other. The wondrous Kenken is composed of significantly more serious matter to significantly enhance one's grey matter. Like Sudoku, even though difficulty may vary from puzzle to puzzle, the rules for playing KenKen (translated as 'square wisdom') are fairly simple. Do not repeat a number in any row or column. The numbers in each heavily outlined set of squares, called cages, must combine (in any order) to produce the target number in the top corner of the cage using the mathematical operation indicated. Now the simply fiendish arithmetical challenge that is sweeping the world can be yours every day of the year, without so much as having to buy a newspaper. The high tech hotness of this splendiferous gizmo will be enough to encourage you to pick it up and give one's cells a decent workout. Featuring a touch backlit LCD screen with stylus and sound effects, one's brain training becomes somewhat, dare we say it, fun. And with the tagline of 'the World's most ADDictive puzzle' (groan), aplenty of brain training you'll be adoing. And that most certainly adds up.