Huh, that's an interesting edge case. If it's solidly mines they would've cleared. That means there is a "6" clue right in the middle of mines and by the current rule of the game it won't ever be revealed.
翻訳: ダンジョンに囲まれた墓はクリックできません
Bug: It seems like when I enter an invalid guess it still counts as a guess but doesn't update to the board.
Describe: When I still have two guesses left I started filling in random letters and trying if it's a valid guess. After a couple of tries I got the game over screen, which is weird because the board isn't finished.