Minesweeper Without the Guessing: Six Patterns Worth Learning

Most lost games of Mine Sweep are lost to impatience, not bad luck. These six patterns turn hopeful taps into certain ones.

People tend to treat Mine Sweep as a game of nerve. Tap, hope, tap again. In fact most boards can be cleared, or very nearly cleared, without a single hopeful tap. What it takes is a small stock of patterns that you recognise on sight.

Here are the six we use most, roughly in the order you will meet them.

1. The number that is already full

If a square shows 1 and you have flagged one mine beside it, it is finished. Every other unopened square touching it is safe. The same goes for a 2 with two flags, and so on.

It sounds too obvious to count as a pattern. It is also the one that people skip. After placing a flag, go round every number that touches it and ask whether it is now full. Half your safe squares come from this.

2. The number that has no choice

The mirror image. If a 3 has exactly three unopened squares around it, all three are mines. Flag them, then go back to pattern one.

Between them, these two rules clear most of an easy board. Everything below is for the moments when they run out.

3. One, two, one

You have a straight wall of unopened squares, and running along it you see the numbers 1, 2, 1. The mines are under the two 1s. The square next to the 2 is safe.

The reason is neat. The 2 needs two mines from the three squares facing it. Each 1 can only have one. If a mine sat in the middle, both 1s would be used up and the 2 could never get its second.

4. One, two, two, one

The longer cousin. Along a straight wall: 1, 2, 2, 1. This time the mines sit beside the two 2s, and the squares beside the 1s are safe. Once you have seen it a few times it jumps out of the board.

5. The one at the edge of a two

This is the general idea behind both patterns above, and it works in places where they do not quite fit. Suppose a 1 and a 2 sit side by side along a wall. The 1 touches two unopened squares and the 2 touches the same two plus one more. Since the shared pair can hold only one mine, the extra square must hold the 2's other mine.

Run it the other way and you find safe squares. Suppose two 1s sit side by side. The first touches only two unopened squares, so its mine is in one of them. The second touches those same two and one more. Its single mine is already accounted for, so the extra square is safe.

It takes longer to explain than to use. Compare two neighbouring numbers, look at which squares they share, and see what is left over.

6. Count what is left

The status line tells you how many mines are still unflagged. Near the end, this number settles arguments the grid cannot. Two unopened squares in a corner and one mine left elsewhere means the corner is clear. Three squares, three mines: flag the lot.

When you really must guess

It happens. Two squares, one mine, no number that can tell them apart. A few things soften the blow:

• Guess early, not late. Losing at the start costs ten seconds.
• A square in the open, far from any number, is often safer than a square beside a 1 that has two candidates. With ten mines in eighty-one squares, an unknown square carries roughly a one in eight risk.
• Never guess while there is still an unchecked number on the board. There is usually one more deduction hiding.

Two things about our version

Your first tap on GridPencil is always safe, and so is every square touching it, so you start with an opening instead of a single lonely number. And on a phone, the Flag mode switch under the board makes taps plant flags, which is safer than trying to long-press.

Mine Sweep has been with us since the early 1990s and it is still one of the best HTML5 games for a short break, because it rewards exactly one habit: looking twice before you tap.