Corner Patterns: The Most Constrained Cells in Minesweeper

A corner cell has exactly 3 neighbors. That tiny neighborhood makes corner numbers incredibly powerful — often a single number is enough to determine every adjacent cell.

Key principle: The fewer the neighbors, the tighter the constraint. Corners are the tightest.

The Three Corner Numbers

Corner “1” — One Mine Among Three

A “1” in the corner means exactly 1 of the 3 neighbors is a mine. On its own, you cannot tell which one. But pair this with any adjacent numbered cell and the mine is usually locatable.

1 ?
? ?

One of the three “?” cells is a mine. If a neighboring number can eliminate one or two candidates, the mine is pinpointed.

Corner “2” — Two Mines, One Safe Cell

A “2” in the corner means 2 of the 3 neighbors are mines. Flip the logic: the remaining cell is guaranteed safe. You do not even need to know which two are mines — any cell that is not a mine is safe, and there is exactly one.

This is one of the most satisfying deductions in the game: click the one cell that must be safe, then flag the other two.

How to identify the safe cell: If any neighboring constraint tells you which cell is safe, click it immediately. If not, look at which of the 3 cells shares constraints with other numbers — the overlapping one is most likely identifiable.

Corner “3” — All Three Are Mines

A “3” in the corner means all 3 neighbors are mines. Flag every one of them immediately. This is the easiest deduction possible — no analysis needed.

3 *
* *

Flag, flag, flag. Done.

Why Corners Chain Into Bigger Deductions

The real power of corners is what happens after you resolve them. Flagging a mine next to a corner cell reduces the effective count of every number sharing that mine. This reduction cascades outward along the wall.

Example chain:

Corner shows “2” → flag 2 mines, click 1 safe cell.
The safe cell reveals a “1” along the wall edge.
That “1” already has a neighboring flag (from step 1), so it is fully satisfied.
Chord that “1” to reveal all its other neighbors.
The newly revealed cells produce further patterns along the edge.

Corner deductions often cascade into solving long wall segments. This is why the strategy guide recommends scanning corners and edges first.

Combining Corner Numbers with Adjacent Constraints

Corner “1” + Adjacent “1” Along the Wall

1 ? ?
1 ? ?

The corner “1” has neighbors: (row1 col2), (row2 col1), (row2 col2). The wall “1” below it has neighbors including some of the same cells. Applying subset logic: if the wall “1”’s mine must be among a subset of the corner “1”’s neighbors, then cells outside that subset are safe.

Corner “1” + Adjacent “2”

1 ?
2 ?

Corner “1”: exactly 1 mine among {right, below, diagonal}.
Edge “2”: 2 mines among its 3–5 neighbors.

The overlap often pinpoints the mine near the corner, which then reduces the “2” and triggers further deductions.

Where to Find Corner Patterns

Literal Board Corners

The four corners of the game board. After your opening click, check all four corners. A revealed corner number is an instant deduction opportunity.

Boundary Corners

Where two boundary lines meet at a right angle. These are not literal board corners but behave identically — the cell at the bend has only 3 unrevealed neighbors.

Island Corners

When a revealed region has a protruding corner, the cell at the tip of the corner has only 3 unrevealed neighbors. Same logic applies.

Common Mistakes

Overlooking Corner “2”

New players often focus on flagging mines but forget that corner “2” also reveals a safe cell. The safe cell is just as valuable — it expands your information.

Not Following Through

Resolving a corner is step one. The real payoff is the chain of reductions that follows. Always look at the newly reduced numbers along the adjacent wall after resolving a corner.

Confusing Cell Counts

An interior corner cell has 8 neighbors, not 3. Corner patterns apply only when the cell is at the actual board boundary (or an effective boundary with all other neighbors revealed). Count the unrevealed neighbors — if there are exactly 3, corner logic applies.

Key Takeaways

Corner Number	Mines	Safe Cells	Action
1	1 of 3	2 of 3	Need more info — combine with adjacent numbers
2	2 of 3	1 of 3	Click the safe cell, flag the rest
3	3 of 3	0	Flag all three immediately

Wall & Edge Patterns — Corners are at the ends of walls.
1-1-Corner Pattern — When corner geometry creates a 1-1-X configuration.
1-3-1 Corner Pattern — A corner variant where mines go at the flanks of the 3.
2-2-2 Corner Pattern — Saturated corner configurations with higher mine counts.
Subset Safe — The mathematical principle behind corner “2”.
Reduction — What to do after flagging corner mines.
All Minesweeper Patterns — Complete visual guide.