Excellent fitness for the mind and energy for the brain. 100 Lighthouse Battleship puzzles 10x10 + 11x11 hard levels and 12x12 + 14x14 very hard levels. 100 Yajilin puzzles 10x10 + 11x11 + 12x12 + 14x14. 50 Calcudoku sudoku puzzles 9x9 hard levels. 50 Calcudoku sudoku puzzles 9x9 very hard levels. 50 Tridoku Sudoku puzzles 9x9 hard levels. 50 Tridoku Sudoku puzzles 9x9 very hard levels. Unique puzzles. + 250 sudokus difficult level that can be downloaded and printed. + 250 maze puzzles that can be downloaded and printed. Only 1 verified solution. All answers are at the end of the book. Exclusive puzzles. The best book for free time and mind exploration. I hope you enjoy the book. Best regards, Basford Holmes