• THE BEST SUDOKU: Every puzzle in this calendar is created by Nikoli, the best Sudoku makers in the world--not a computer--to balance toughness and solvability and keep you hooked.
  
  
• TRAIN YOUR BRAIN: The week begins with the easiest puzzles and the difficulty increases day by day. Just in case you need them, solutions are printed on the back of the pages.
  
  
• NOW PLASTIC-FREE!: Page-A-Day(R) Calendars are environmentally friendly! Printed on responsibly sourced paper and 100% recyclable, with sturdy cardboard backers.

NIKOLI is the Japanese puzzle and game company that's been nurturing and developing sudoku for over thirty-five years. They hold the trademark on sudoku in Japan, and supply 100 percent of the puzzles published in Japanese newspapers and magazines.