Love It - Needs 1 Improvement
There is an issue with the unmarked tiles being nearly impossible to see on large nearly complete puzzles. This is due to the fact that there's very subtle grey shading on the tiles marked with an X. When you are looking at a sea of light-shaded tiles, a single white tile becomes invisible. Developer refuses to update the game by giving players the option to have unmarked tiles a different color. It would be such a simple fix, and would be such a huge improvement.