Minesweeper Patterns: 1-2-1, 1-2-2-1 and 50/50 Guessing

The 1-2-1 pattern

When three numbers read 1-2-1 along a straight edge with exactly three unknown tiles beside them, the solution is fixed: the two mines sit under the two 1s, and the tile under the 2 is always safe.

Verify it by counting. The middle 2 needs two mines and only sees three unknown tiles. The outer 1s each need one mine and share part of that neighborhood. The only arrangement that satisfies all three numbers puts a mine under each 1 and leaves the middle tile safe.

Because this rule is proven rather than guessed, you can open the tile under the 2 immediately and flag the two outer tiles with total confidence.

• 1-2-1: mines on the ends, safe in the middle.
• Works along any straight edge (top, bottom, left, or right).
• Also appears on the wall of a wider revealed region.

The 1-2-2-1 pattern

The 1-2-2-1 pattern is the four-tile sibling: four numbers read 1-2-2-1 with four unknown tiles beside them. The two mines sit under the two 2s, and the outer tiles — under the two 1s — are safe.

This shape matters because it resolves two safe tiles and two mines in one look, often unlocking a large cascade on expert boards.

• 1-2-2-1: mines under the 2s, safe under the 1s.
• Count-check it before trusting it on an irregular edge.

Corner and edge shapes

Corners are the strongest single clues in minesweeper because a corner tile only has three neighbors. A 1 in a corner with one unknown neighbor means that neighbor is a mine; a corner 2 with two unknown neighbors means both are mines.

Along an edge, a 1-1 pair against two unknown tiles looks like a classic trap, but check for a third clue first — an adjacent number often breaks the tie.

• Corner 1 = the single unknown neighbor is a mine.
• Corner 2 = both unknown neighbors are mines.
• Edge 1-1 pairs are often resolved by a neighboring number.

The 50/50 and how to guess smart

A 50/50 is a position where two different mine layouts satisfy every visible clue. In that case no amount of logic finds a guaranteed safe tile — you must guess. These occur most often along edges and in the last few tiles of a board.

When a guess is forced, choose the tile that gives the best information if you survive: the tile that opens the largest unexplored region, or the tile with the lowest mine probability from counting remaining mines.

If the board is already decided by the guess (for example a late 50/50 that settles the whole game), guess immediately rather than wasting time clearing safe tiles. If the 50/50 appears early, play every guaranteed move first so the guess is the last unknown.

• Count remaining mines against the remaining unknown region.
• Prefer the guess that opens the most new area.
• Play all logical moves before a forced guess.
• Guess early when the 50/50 decides the whole board.