Lesson 5 of 7
Patterns
3 min

The 1-2 Pattern in Minesweeper

The 1-2 is the pattern behind the longer ones: the 1-2-1 and the 1-2-2-1 are both built from it. Learn to read it from the 1, and it works along any straight edge, in either direction.

Step 1 of 4

A 1 beside a 2
The 1 in row 4, column 1 touches two hidden cells, in row 3, columns 1 and 2: exactly one of them is a mine. The 2 beside it touches those same two cells, plus the starred one. The shared cells can give the 2 only one mine, and it needs two. So the third cell is a mine. This is the 1-2 pattern.
Flag the mine
The 1 still doesn't say which of its two cells is the mine. The 2's extra cell is certain.
Your move
Flag the mine the 1-2 proves.
Away from the wall
A 1-2 works anywhere along a straight edge. Find the 1 in row 4, column 4 and the 2 on its right. The 1 has one mine among its three hidden cells; the 2 shares two of those and has one of its own. The shared pair holds at most one mine, so the 2's own cell is a mine. And since the 1's mine is in the shared pair, the 1's own cell, on the far side, is safe. Both cells are starred: which is which?
Your move
Flag the mine and open the safe cell this 1-2 proves.
Find one yourself
Patterns don't care about direction: read a 1-2 from its 1, whichever way it runs. This board has a 1-2 along its edge. No stars this time.
Your move
Find the 1-2 on this board and flag the mine it proves.

What you learned

A 1 beside a 2 along a straight edge: the cell only the 2 touches is a mine.
Away from a wall, the cell only the 1 touches is safe as well.
It works in every direction. Read it from the 1.
It only holds when both numbers touch nothing hidden but the cells along the edge.