If most Sudoku puzzles are too easy for you - Get this book of 200 Hard Puzzles for a real challenge. IMPROVE YOUR SKILLS You can practice solving puzzles that require: X-Wing (20), XY-Wing (70), XYZ-Wing (20), XY-Chain (70), and Coloring (20) logic techniques. A puzzle may not seem very difficult as you start it, but just wait 'til you reach the spot that requires an advanced technique! LARGE PRINT - 2 big puzzles per page give you room for listing candidates. Even the solutions at the back are large print. EXTRA WIDE INNER MARGINS make it easier to fold back the book or tear out pages when you are on-the-go.STURDY WHITE PAPER increases visibility and holds up well when you erase.