Step 1 of 5

Reading Numbers

Every number is a count of the mines touching it. Two moves follow from that.

The rule of thumb: A number counts the mines in the 8 cells around it. Full of flags: open the rest. As many hidden cells as mines: flag them all.

A number counts the mines in the cells around it: up to 8, fewer on an edge or in a corner. Blank open cells are zeros. Nothing around them is a mine, which is why they open a whole area.

Move one: if a number still needs as many mines as it has hidden cells around it, they are all mines. Flag them. Move two: if a number already touches all its mines (count its flags), every other hidden cell around it is safe. Open them.

These boards fall to those two moves alone. Work outward from the opening, one number at a time.

Where to look: Numbers on the rim of the opened area with only one or two hidden cells next to them. Corners are the easiest: a corner cell has just three neighbors.

Worked example

A real position from a 8×8 board with 10 mines. Purple: the numbers the reasoning rests on. Dashed: the cells in question. Green: what it proves.

The 2 at row 6, column 5 (purple) still needs 2 mines, and exactly 2 hidden cells touch it (dashed).

So they are all mines: flag them (green). Now the 1 at row 4, column 5 touches all its mines, with hidden cells still around it (dashed).

The 1 at row 4, column 5 already has its mine flagged, so every other hidden cell touching it is safe. Click the 1 to open them all at once: that’s a chord.

Practice it ↓