1. Might be also nice to handle 0-0 case separately and grey out all those letters both in the guesses on the board and perhaps in a separate keyboard as well.

1. Might be also nice to handle 0-0 case separately and grey out all those letters both in the guesses on the board and perhaps in a separate keyboard as well. 2. Can go one step further, e.g. if a guess has X-0 and all there's only X cells that are not greyed out (see above), mark them as green in all correct guesses on board. 3. After these two steps, step 1 can be applied again since there will be more such cases where it can be applied. You might argue that it steals from the game, but I'd disagree - it leaves the high level strategy to the player while saving them from dealing with the boilerplate. A very good example of that is Good Sudoku game (app), where they've tried to innovate on classic sudoku interface for similar purposes - I highly recommend checking it out since it's somewhat close to this game in some regards.