Sudoku Free is an app that brings the popular game of Sudoku to life. As the name suggests, this app is completely free to use and features more than 15,000 puzzles to solve. One of the great things about this version of Sudoku is that there are eight difficulty levels in total, making it possible for people of all capabilities to get in on the fun. There is even a handy hints feature for those who need a little extra help and this helps to prevent the game becoming too frustrating.