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KMines does not have a hints+solver mechanism, like KPatience has. I propose creating such an ability, which would be able to flag mines or uncover fields if the player would be able to do so himself without guessing (ie using visible information).

A demo mode can be constructed on top of this, since that would mostly consist of doing correct moves.

The statusbar of KPatience could also be used in KMines, showing information like "This game cannot be solved without guessing" and "No certain moves left, you'll have to guess".

To see how difficult making a solver is, I created one. The source is available at http://www.matthijstijink.nl/mines.tar.gz. I hacked this together in 45 minutes, so it is certainly feasible.
(Notes on control: left click for solving/guessing one square, right click for auto-solving twice per second, space for solving all possible squares)