I love this app but after the latest update it does not store the state of my Sudoku correctly if I pause the puzzle. So when I am in a puzzle, have to do sth else, and then start again I have to redo 5-10 of the last steps.
Another point of improvement would be to make an extra level between difficult and expert. For a long time now for me the Difficult level is very easy, but the Expert level is too hard because you need to recognize the complex patterns. A level inbetween would make the game more fun again for me.