Almost Summer, so it's time for a Calcudoku Holiday Puzzle Book, with 250 puzzles of all types and sizes: puzzles from zero, twin puzzles, extra large puzzles (up to 12x12 ) - so whether you're looking for a quick fix, or hours of puzzling on a single puzzle, it's all here in this book Solving a Calcudoku takes not just logic reasoning (as in Sudoku), but also basic math skills, making it a much more interesting and satisfying puzzle. The puzzles are printed large and on high-quality paper, so there is plenty of space for notes. Included are a description of the rules, explanations for the puzzle variations, and all solutions. Puzzles are rated between 1 star (easy) and 5 stars (difficult), divided into 3 chapters: 50 easy puzzles, 150 medium puzzles, and 50 difficult ones. You can even submit solutions for the difficult puzzles in this book at www.calcudoku.org, and score 10 points for each correct solution