A pattern is a proof, not just a sequence
A Minesweeper pattern combines neighboring numbers to identify forced mines and safe squares. Along the exact straight edges shown below, 1–2–1 puts mines in the outer two squares; 1–2–2–1 puts mines in the middle two. These rules depend on which covered squares each number touches.
Before applying either pattern, check that the numbers have no additional unaccounted-for covered neighbors on their other sides or beyond the ends. The practice boards are complete mini boards, so there is nothing hidden outside their edges.
New to counting neighbors? Start with the first-moves lesson. For these examples, letters name covered squares; the numbers underneath are already open.
The 1–2–1 pattern: mines outside, safe inside
Place covered squares A, B, and C above the numbers 1, 2, and 1. The left 1 touches A and B. The middle 2 touches A, B, and C. The right 1 touches B and C.
- Compare left with middle. A and B contain one mine together. A, B, and C contain two. The extra square C must contain the extra mine.
- Compare right with middle. B and C contain one mine together. Adding A raises that count to two, so A must also be a mine.
- Clear the center. A and C account for both mines. B must be safe.
Try the 1–2–1 pattern
Only A, B, and C are covered. All three numbers face the same straight edge. This is the entire practice board.
Step 1 of 2
Find the two certain mines. Select both squares to flag them, in either order.
Select squares to answer the prompt. Mistakes are safe here.
Read the solution and reasoning
- A and C are mines. A + B accounts for one mine, but A + B + C accounts for two, so C is a mine. Comparing the right 1 with the 2 proves A is a mine too.
- B is safe. Both outer 1s and the middle 2 now have all of their mines accounted for.
In this exact 1–2–1 edge, the outer squares are mines and the middle square is safe. Check the surrounding squares before applying it elsewhere.
The 1–2–2–1 pattern: mines inside, safe outside
Now there are four covered squares, A through D, above 1, 2, 2, 1. Work from the ends rather than guessing between the two central clues.
- Start on the left. The 1 counts A and B; the neighboring 2 counts A, B, and C. Their difference forces C to be a mine.
- Repeat on the right. The right 1 counts C and D; its neighboring 2 counts B, C, and D. Their difference forces B to be a mine.
- Open both ends. With B flagged, the left 1 needs no other mine, so A is safe. With C flagged, the right 1 proves D safe.
Try the 1–2–2–1 pattern
A, B, C, and D are the only covered squares along this edge. There are no extra covered neighbors outside the diagram.
Step 1 of 2
Select the two squares that must contain mines, in either order.
Select squares to answer the prompt. Mistakes are safe here.
Read the solution and reasoning
- B and C are mines. Comparing the left 1 with its neighboring 2 forces C; comparing the right 1 with its neighboring 2 forces B.
- A and D are safe: B satisfies the left 1, and C satisfies the right 1. Neither end can contain another mine.
In this exact 1–2–2–1 edge, flag the middle pair and open the two ends. The shape of the covered area matters as much as the numbers.
Subtract known mines before comparing
A displayed number counts all adjacent mines, including any you have already correctly flagged. For reasoning about the remaining squares, subtract those known mines.
A 3 touching two known mines needs one more mine among its other covered neighbors. It acts like a 1 for that remaining group; the number displayed on the board stays 3.
This can reveal a familiar pattern inside a group of larger numbers. Recheck the neighbor sets after subtracting: having remaining counts of 1, 2, 1 is only useful if the remaining covered squares also form the right shape.
You can rotate or mirror either example. Adjacency stays the same, so the reasoning still works. You cannot add extra covered neighbors and assume the result will stay the same.
When the pattern does not apply
Suppose the left 1 in the first example touches an extra covered square X beyond A. It now counts X + A + B, while the middle 2 counts A + B + C. You can no longer subtract the first group from the second to force C: the groups do not contain the same shared squares.
Likewise, a wrong flag makes your remaining-mine counts wrong. Check the original reason for each flag before using it in a deduction.
When no certain move is visible, scan other edges and consider the total number of remaining mines. Some positions still require a guess. Pattern recognition makes logical moves easier to spot; it does not make random boards guess-free.
Once your flags are certain, use chording to clear the safe neighbors without opening them one at a time.