Minesweeper Coach
Guaranteed safe rule

All Mines Accounted For

If a numbered clue already touches exactly that many correctly marked mines, every other adjacent covered cell is safe to reveal.

clue number−adjacent flags= 0 mines left
Minesweeper Coach showing a clue 1 beside one flag and highlighting row 2, column 1 as guaranteed safe.
This is the actual Minesweeper Coach result for the example below. The outlined cell is safe.
Step-by-step proof

Why the highlighted cell is safe

  1. The corner clue is 1.

    Exactly one of its adjacent cells contains a mine.

  2. One adjacent cell is already flagged.

    The clue’s complete mine requirement is accounted for: 1 − 1 = 0.

  3. No other adjacent covered cell can be a mine.

    Row 2, column 1—and the other covered neighbor beside that clue—can be revealed safely.

What to learn next

If the remaining mine count equals the remaining covered-cell count, use All Covered Cells Are Mines. If neither direct rule works, compare overlapping clues with the Subset Rule.

Try this rule in the Solver