In Sudoku Challenge, players take on their friends in this head-to-head version of a modern-day classic. Or, enjoy some addicting "brain food" as you sharpen your skills as a single player. Serious fun for one to four players. Also in the box comes the bonus game Zoodoku: Both kids and adults will be hooked on logic when they play Zoodoku. This game variation of Sudoku Challenge features colorful animals native to Japan in place of numbers.