Minesweeper Patterns

A pattern is a familiar group of numbers along the edge of an open area that always resolves the same way. Experienced players don't recount every cell; they recognize the shape and click. Below are five patterns that cover most situations on any board size. In the pictures, a yellow frame marks the conclusion: an empty frame means safe to open, a frame with a flag means a mine.

1-1 against a wall

A 1 in a corner or along an edge sees only two covered cells, and one of them is a mine. The 1 next to it sees the same two cells plus one more. Its mine is already among the first two, so the third cell is safe.

1-1 at the left edge: the third covered cell along the top is safe.

1-2

A 2 next to a 1 shares some cells with it, but the shared cells can hold at most one mine, because that is all the 1 allows. So the 2's second mine sits in the cell the 1 cannot see.

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1-2: the far cell above the 2, outside the 1's reach, is a mine.

1-2-1

One of the most common shapes on Expert. A row of covered cells above the numbers 1-2-1: the mines sit above the 1s and the cell above the 2 is safe. If the mine were above the 2, both 1s next to it would already be satisfied, and the 2 would be missing its second mine.

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1-2-1: mines above the 1s, everything else is safe to open.

1-2-2-1

The same idea with two 2s: the mines sit directly above the 2s, and the cells above the 1s and further along the edge are safe.

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1-2-2-1: two mines above the 2s.

Subtracting flags

The most useful trick of all: when a number already touches a known mine, subtract it. A 3 next to one flag behaves like a 2, a 2 next to a flag behaves like a 1. After subtracting, almost any messy edge turns into one of the patterns above.

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The flag on the left turns the 2 next to it into a 1, and on the right a 2 beside a 1 is a plain 1-2.

Common mistakes

A pattern only works when every cell the numbers can see is accounted for. The most common slip is missing one more covered cell to the side or below, and then a 1-2-1 is no longer a 1-2-1. The second is forgetting a flag you placed by mistake. If a conclusion contradicts a neighboring number, don't click: recheck the flags around it, the wrong one usually turns up right away.

How to practice

Turn on No-guessing on Intermediate. Every move on those boards follows from the numbers, and if you get stuck, the Hint button shows a cell and tells you whether it took one number, two numbers or a full search to find it. After a few dozen games the patterns start jumping out at you. Next up: what to do when the numbers really say nothing.