If you back yourself into an unsolvable corner, Good Sudoku lets you know and can rewind your moves to the first spot where the puzzle can still be solved. There’s also an introduction to the basics ...
This year, competitors were required to solve nine Sudoku puzzles within a 30-minute time limit. Morinishi and Endo both solved all correctly in 20 to 29 minutes. Endo attributed his speed to ...