Pretty much improved Minesweeper. Would be nice if clicking on a flagged square didn't immediately trigger it, as missclicks happen, and you've already guessed that's a mine, so you wouldn't want to click it without unflagging it. Except for farming turtles.
Dragging (both board and upgrade screen) seems a little sensitive, although not much, and it's not much of a problem. It just feels a little fluttery.
Agreeing with other comments about zoom of upgrade screen and mine contrast (would be nice to add some red to detonated/broken mines to make them more similar to flags, which makes it easier to count them together).