Visual logic is reversed

[yspreen]

If you don't read the text fully, from the visuals only you get the impression to flag all false fields, not all true ones.

The strictly equal fields are marked with a checkmark (good) which should be the opposite of a mine (bad).
So when those are no mines, surely all true fields are no mines, right? And thus you have to mark all other fields (the false ones) with a flag, because there is a mine under them.

The visuals for the results were also very confusing to me, and I think there should be a legend.

[slikts]

There sort of is a legend; the score panels have a tooltip that explains what the icons correspond to – flags, hits and misses.

Flagging hundreds of fields would be very tedious, which should be a hint that it's not intended.

I suppose one solution could be to use some other icon than a flag to mark cells, but I'm not sure what icon would represent a potential checkmark. A checkmark with a question sign maybe.

[yspreen]

I think changing the default checks would do the trick.
I would propose you stack two icons on top of eachother: Flag with 50% opacity and the checkmark on top

[yspreen]

Maybe like this?

[slikts]

Thanks, I like this idea, but it might be difficult to implement well, since the emojis look differently in different systems. Maybe instead of having them overlap, they could be in the opposite corners of the cell.