Minesweeper deduction

Minesweeper deduction is the classic minefield without the part that needs luck. The board is already uncovered; nothing you tap can explode. Your job is the other half: mark where the mines are — and do it so that it can be proved.

The rules

Some cells are uncovered and carry a number. It says how many of the eight neighbouring cells hold mines, diagonals included. A 0 means none. Every other cell is covered; some hide a mine, the rest do not.

The number above the board is the total. It says how many mines lie in the field altogether — and it is itself a clue, not just a counter.
Only mark what is certain. Tapping a cell places a mark, a second tap takes it back.
It checks itself as soon as you have marked as many cells as the count above. Nothing happens before that — you can rearrange in peace.

Every task is solvable without guessing and has exactly one solution. If you are stuck, a rule is missing — not luck.

An example, step by step

A real 6×6 board with four mines, solved with the same rules that apply in the game. A red cell has been identified as a mine, a cell with a green dot as safe — both colours keep their meaning in the light and the dark appearance. Each step names the technique, the reason, and what follows from it.

Step 1The rest are safe — The 0 in row 5, column 5 says it outright: none of its neighbours hides a mine. That makes these safe: row 4, column 4; row 4, column 5; row 4, column 6; row 5, column 6; row 6, column 4; row 6, column 5; row 6, column 6.

Step 2The rest are mines — The 2 in row 5, column 4 has 2 covered neighbours left, and 2 of its mines have not been found. There is no choice left. That puts mines in row 4, column 3; row 5, column 3.

Step 3The rest are safe — One mine is already marked around the 1 in row 6, column 3, and it has no more to give. The remaining 2 neighbours are therefore safe. That makes these safe: row 5, column 2; row 6, column 2.

Step 4Subset rule — Every covered neighbour of the 1 in row 1, column 2 is also a neighbour of the 2 in row 2, column 2. Of those, the 1 claims one mine, and the 2 is missing no more than that. The 2 cells outside that shared area are therefore safe. That makes these safe: row 1, column 3; row 3, column 3.

Step 5The rest are mines — The 1 in row 1, column 2 has a single covered neighbour left, and its last mine has not been found. There is no choice left. That puts a mine in row 1, column 1.

Step 6Mine count — Of the 4 mines on the board 3 are marked, and one is still missing. The 2 in row 2, column 1 already claims what is left, so nothing outside its neighbourhood can be a mine: the 13 cells it does not touch are safe. That makes these safe: row 1, column 4; row 1, column 5; row 1, column 6; row 2, column 4; row 2, column 5; row 2, column 6; row 3, column 4; row 3, column 5; row 3, column 6; row 4, column 1; row 4, column 2; row 5, column 1; row 6, column 1.

Step 7The rest are mines — The 1 in row 2, column 3 has a single covered neighbour left, and its last mine has not been found. There is no choice left. That puts a mine in row 3, column 2.

Step 8The rest are safe — 2 mines are already marked around the 2 in row 2, column 1, and it has no more to give. The one remaining neighbour is therefore safe. That makes row 3, column 1 safe.

The techniques by name

These are the same names that appear above a hint you buy in the game. Read them here, take a hint there, and you meet the same word again.

The rest are mines. Where a number has exactly as many covered neighbours as it is still missing mines, all of them are mines. The most common step there is.
The rest are safe. The reverse: once all of a number's mines are marked, every further neighbour is safe. A 0 is the special case where that holds immediately.
Subset rule. Where one number sees only cells a second number sees too, the two can be set against each other. What the second one sees on top of that is then settled — even though neither number would get anywhere on its own. This is the step most people get stuck on.
Mine count. Counting in the total above the board: once every mine is found, all the rest is safe. And where a single number already claims every mine still missing, none can lie outside its neighbourhood. This rule works across the whole board, not just locally.
Trial. On the hard tier only: you assume a mine on one cell. If that leads to a contradiction, the cell is safe — and the other way round.

Practise it yourself

In practice mode you can play Minesweeper deduction on its own, as often as you like and on the tier you choose. None of it counts towards a leaderboard — it is the place to try things out.