# What do I do when two squares are equally valid?

The following happened playing Minesweeper:

How do I figure out which square to click?

• So, which square was it? Commented Oct 16, 2016 at 18:11
• Might I suggest Simon Tatham's Mines, which is a minesweeper implementation that is guaranteed to always be logically solvable? chiark.greenend.org.uk/~sgtatham/puzzles/js/mines.html Commented Oct 16, 2016 at 21:32
• Reversing the duplicate direction because I believe this question (and answers) are of higher quality than the current dupe target. See this meta: On ending Chronological Oppression with respect to the matter of Question Duplication
– Robotnik
Commented Oct 17, 2016 at 9:30
• I haven't played Minesweeper in a long time and I can't check it right now, but I believe that planting the final flag (instead of clicking a hopefully empty square) solves the game automatically if it is the right one. So you could try putting a flag in it and if nothing happens remove it and put it in the other.
– Ivo
Commented Oct 17, 2016 at 14:12

## There is no way to logically determine which square to pick here

I'm afraid there's no special trick or anything to solve this situation reliably. All the available information is clearly displayed for you, and there's an equal chance of either square having the mine. Minesweeper simply isn't designed to be logically solvable 100% of the time. This is why sides and corners are somewhat dangerous, though the situation can happen in other ways, too.

All you can do is guess and hope for the best.

• I've always hated when the game boiled down to this scenario. When its in the corner like this, I would always choose the corner piece, but there's no guarantee. Commented Oct 16, 2016 at 3:25
• I always try to pick one option as soon as I see that it boils down to chance... I wouldn't want to solve the rest of puzzle only to come back to this in one the end and then lose because of bad luck
– Lope
Commented Oct 16, 2016 at 11:25
• Yeah, you just pick all the luck tiles first so you don't waste your time. There is no logical solution here. Commented Oct 16, 2016 at 16:20

## Logically, no

Either of those squares can contain a mine, as you have noted. So there is no way to determine which one.

## Statistically, maybe

Because the last mine left is either in the upper-left corner or the square to its right, an answer to another Mine Sweeper question may help a bit, though.

If a mine is under the first clicked tile, it is moved to the upper-left corner, if the upper left corner is occupied, the mine moves to the right of the corner tile.

That is sourced to someone who reverse engineered the game.

### Statistical analysis

So if you happened to have landed on a mine on your first click, that mine has been moved to the upper-left corner. In this case, it can't have been moved to the square to its right, since that would mean the upper-left corner was already occupied by a mine and you would have a mine in both squares, but there's only one mine left in your example.

So if you did not land on a mine on your first click, you have a 50% chance for either square to contain a mine. If you did land on a mine on your first click, the mine will be in the upper-left corner. Since your board has 99 mines on a 16×30 grid, there's a 99 in 480 chance of having done so.

Combining these, you have about a 60% chance of the mine being in the upper-left corner and a 40% chance of it being in the square next to it.

• That is a really dirty game tactic. Though I can understand not triggering the minefield on the first click, at least move it to a random spot then. Awesome answer though :) Commented Aug 3, 2017 at 15:12
• @Flater, but it does make sense. I've always noticed that you never first click on a bomb. It's the games way of giving you a legitimate starting point, plus it's annoying to lose on your first click of what is suppose to be a game of logic with a little chance mixed in.
– RLH
Commented Sep 22, 2017 at 14:06
• @RLH: That's why I said "at least move it to a random spot". My issue isn't that the first click is guaranteed to be safe (I agree that it would suck losing a game on the first click), it's that when this is triggered, the mine is always moved to the top-left spot. Commented Sep 22, 2017 at 14:23
• @Flater, ah I see what you mean.
– RLH
Commented Sep 22, 2017 at 20:09
• This is so awesome! The situation could have occurred anywhere and the answer would have just been that either choice is equally valid, but exactly here there is only one clearly preferable tile. Commented Aug 19, 2021 at 18:18