So you think you're tough enough? This collection of puzzles was created for only bravest sudoku solvers. Many may attempt to master them but only the sharpest minds will succeed. So put your sudoku skills to the ultimate test and see if you're tough enough for these dangerously devious puzzles. But if you find yourself pulling out your hair in frustration, don't say we didn't warn you. Features: - 100 very challenging puzzles- Edited by legendary "New York Times" crossword editor Will Shortz""- Big grids with lots of space for easy solving