[ufo]

The Sudoku app I currently play is this one: https://f-droid.org/en/packages/org.secuso.privacyfriendlysu... (found by searching Sudoku on F-droid)

My only beef with it is the difficulty. I feel that Hard is easily solvable without guessing but Challenging invariably forces me to resort to guessing at least once. (I believe that's the logic their underlying library uses). How does your app determine the difficulty of the puzzles?