Step 4 of 5

Corners & Endgame

In the last corner of the board, count the mines that are left.

The rule of thumb: Use the mine counter: when the numbers you see need every mine left, all other hidden cells are safe, even corners no number touches.

The 💣 counter shows the mines left: total mines minus your flags. Near the end, that number is a clue of its own.

If the numbers you can see need every mine that’s left, no other hidden cell can hold one. That clears pockets no number touches, like a corner walled off by flags. And if the hidden cells left equal the mines left, they’re all mines.

It only works when every flag is right (that’s the next step). These boards can’t be finished without counting.

Where to look: Hidden corners and pockets no open number touches. Compare the counter with what the nearby numbers still need.

Worked example

A real position from a 8×8 board with 11 mines. Purple: the numbers the reasoning rests on. Dashed: the cells in question. Green: what it proves.

The counter says 1 mine left, and the 1 at row 1, column 6 (purple) still needs 1. The dashed cells don’t touch it, and no open number touches row 1, column 8.

Only 1 mine is left, and the 1 at row 1, column 6 needs all of them, so every hidden cell not touching it is safe.

Practice it ↓