I imagine this feature to be similar to "show solution" (as in a button relevant to most/all puzzles), except instead of showing the solution, somehow indicate to the user either:
-all of the partially filled in grid is correct so far
-at least one thing is incorrect
Basically I emulate this functionally by repeatedly showing the solution, then undoing, and compare (with my eyes) my partially filled puzzle with the solution
I imagine this feature to be similar to "show solution" (as in a button relevant to most/all puzzles), except instead of showing the solution, somehow indicate to the user either:
-all of the partially filled in grid is correct so far -at least one thing is incorrect
Basically I emulate this functionally by repeatedly showing the solution, then undoing, and compare (with my eyes) my partially filled puzzle with the solution