Step 2 of 5

1-1 Pattern

Two numbers, one mine between them, and a safe cell for free.

The rule of thumb: When one number’s mine must sit in cells a neighbor number also touches, it counts for both: the neighbor’s other cells are safe.

Sometimes no single number tells you anything. Then read two neighbors together. If every hidden cell where the first number’s mine could be also touches the second number, that mine counts for the second number too.

So when that mine is all the second number needs, its other hidden cells are safe. The classic shape is two 1s side by side along a wall: the cell past the second 1 is safe.

Every practice board here stalls without it, even with the 1-2 Pattern and the mine counter.

Where to look: A 1 next to a 1 (or a 2 next to a 2) along a straight edge of hidden cells, especially against a wall.

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. Amber: the hidden cells the two numbers share.

The 1 at row 2, column 1 and the 2 at row 2, column 2 (purple) share the amber cells. The 1 at row 2, column 1 needs 1 more mine, and it has to be in there. What about the dashed cell, touching only the 2?

Every hidden cell around the 1 at row 2, column 1 also touches the 2 at row 2, column 2, so its 1 more mine is in those shared cells. That’s all the 2 still needs, so its other hidden neighbors are safe.

Practice it ↓