Why are there no options for marking the grids that...

Why are there no options for marking the grids that have no color with an x. I have played these kinds of puzzles on other websites and they have the option of putting an x in the empty grids, this makes the game more enjoyable and less confusing. I love playing nonogram puzzles and your site has a large quantity and variety, so I hope you can add this feature to the puzzles.