Also known as noughts and crosses, this puzzle has existed in some form for decades, and it has recently experienced a wave of popularity under the name kurosu. There is only one rule: No more than two Xs or Os can be next to each other in a given column or row. Kurosu promises a fresh challenge for sudoku fiends and logic lovers. With Posh Kurosu, you get a stylish and portable package that features a hidden spiral bound spine and rounded corners--making it accessible and the perfect gift for any puzzler.