World`s Hardest Sudoku for Android
Yes it is difficult but there is a 2 x 2 that might truly be the world's hardest Sudoku. It is here on Google play, just search SUDOKUit. If you can solve the 5th and 6th level you have forward thinking skill that are above normal. It only takes a few seconds to play. I can solve the 3rd and 4th levels
by D####:
It isn't the hardest sudoku...