200 Sudoku Challenges - Testing Your Brain To Keep You Young - Hard Difficulty Volume 2. This Book Contains 200 Hard Sudoku Puzzles with answers, for those Sudoku puzzlesSudoku Challenges provides you with 200 Sudoku puzzles to test your brain to keep you young.This volume gets you started into the fascinating and addictive world of Sudoku. You are joining a family of millions of people worldwide who enjoy challenging themselves everyday.At the start of the Sudoku Challenges puzzle book you will find a brief introduction to the rules of Sudoku if you don't already know them.When you get started on the puzzles you will see that at the top of each puzzle there is a difficulty rating - the higher the number the harder the Sudoku challenge.There are 4 sections of 'Hard' Sudoku challenges but at the end of the book there are 8 Sudoku challenges that we would describe as very hard difficulty. This is to get you in training and ready for the next book in our series.When you have completed a Sudoku challenge you will find the answers for each section at the end of the book - so you can check how well you have done....or give yourself a clue if you get stuck. Enjoy and good luck!Before you get started it might be worth just checking that you understand the simple rules of Sudoku. They are easy to get to grips with, but the real challenge is implementing them throughout the challenges.Here are the 6 basic rules of Sudoku:1.Each Sudoku puzzle has only one valid solution. 2.Each puzzle can be considered solved correctly only when all 81 boxes contain numbers whilst the other Sudoku rules have been followed.3.At the start of a game of Sudoku, some boxes will have numbers pre-filled for you. You are not allowed to change these numbers in the course of the game - that would make it far too easy!4.Each column must contain all of the numbers 1 through 9 and no two numbers in the same column of a Sudoku puzzle can be the same.5.Each row must contain all of the numbers 1 through 9 and no two numbers in the same row of a Sudoku puzzle can be the same.6.Each block must contain all of the numbers 1 through 9 and no two numbers in the same block of a Sudoku puzzle can be the same. Sound simple? Well the best way to learn is to have a go and in this book you have 200 Sudoku challenges to complete. Good luck!