Kenken game for summer fun

As most of you are taking a break from math or school work, here's a little (addictive) math game to play online or as printed version: Kenken.

In it, you have to place the numbers in the grid kind of like in Sudoku so that no number appears twice in the same row or column, BUT there's an additional twist: it gives you "cages", and the numbers within a particular cage have to work to a given answer with a given math operation (either addition, subtraction, multiplication, or division).

KenKen practices logical thinking and is, I think, more fun than Sudoku.

It's easier to understand if you go see and try it yourself. The smaller sizes, such as 4x4 game, are great for kids, and the larger ones are good for us adults or older students.

• Kenken.com has nice Kenken puzzles online plus instructions, but only one for each size.

• MathDoku.com has an unlimited number of Kenken puzzles to play online in three sizes and several difficulty levels.