Keen: Request a "Correct so far" feature

[sueloverso]

I would like an option on the drop down (with New Game, Restart, Show Solution, ...) where I could check my answers so far.

Similar to when it shows red if the arithmetic is wrong it could show red on incorrect solutions.

I often play 9x9 or difficult levels and would like to check before going far down an incorrect path and then hitting "undo" many times.