I like spending every single moment on playing Best Sudoku, it's a new application I've just found and am addicted already! It's great for beginners and advanced players, has 5 difficulty levels, from very easy to extremely difficult. Undo/ redo and auto-save functions! Everything is clean thanks to very good graphics. Check it out!! https://play.google.com/store/apps/d...n.sudoku&hl=pl