Just how hard can Sudoku be? Well a blank Sudoku grid would give you 6,670,903,752,021,072,936,960 possible combinations to correctly complete the puzzle as there is only one solution. Recognising that you have other thinks to do with your life such as sleeping, eating, maybe relationships and, of course, that bus to catch at 9.30am our hard Sudoku puzzle won't take the rest of your life to complete. And the next life as well. No, its hard, but not impossible. If you do manage to complete it there is a further expert level, however if it all gets too much, put the kettle on, and try one of our easier Sudoku challenges. Some are printable so you can print them off and take them to bed before you take that much deserved rest.