The book contains 400 excellent No Four in a Row puzzles 11x11. Medium puzzles 200 - Hard puzzles 200 - All riddles have only 1 solution. - 2 puzzles per page. - The font size is correct you will not have to strain your eyes when solving puzzles. - High quality paper and print (all puzzles read well, easy to write with pen and pencil without worry of bleed-through). No Four in a Row is played on a rectangular or square grid. Some cells of the grid contain ‘X’ and ‘O’.The task is to fill in the grid so that four consecutive identical symbols never appear in any row, column or diagonal.