The two-player game of logic and deduction nails mathematical reasoning, but yet remains so simple that kids want to come back to it again and again. One player uses the four colored pegs to make a code that his opponents must replicate in 10 moves or less. Make the game as difficult as you want by using multiple pegs of the same color or by leaving peg holes empty. Code-breaking is a great way to teach the foundations of algebra, and is also a brain-bending good time! (Pressman Toys, $9.99)