Minesweeper without the guessing, and The Kid’s Treasure Map

How to play Minesweeper: the rules in a minute

A Minesweeper board is a grid of covered squares, and some of them hide mines. Click a square to uncover it. If it’s a mine, the game is over. If it isn’t, it shows a number: how many mines touch it, in the 8 squares around it, corners included. A square with no mines around it is a 0, and the game opens all its neighbors for you, which is why one lucky click can crack open a whole region.

You win by uncovering every square that isn’t a mine. Flags are optional: right-click a square to mark a mine you’re sure of, so you don’t click it by accident. Windows Minesweeper came in three sizes: Beginner, a small board with 10 mines; Intermediate, 16 × 16 with 40; and Expert, 30 squares wide and 16 tall with 99. It also made sure your first click was never a mine, which is the kindest thing it ever did for you.

A short history of Minesweeper

The idea is older than Windows. Mined-Out, written by Ian Andrew for the ZX Spectrum in 1983, had you crossing a minefield with only a count of the mines beside you to go on. The version everyone knows is Microsoft’s Minesweeper, made by Robert Donner and Curt Johnson. It first came out in 1990, in an Entertainment Pack of extra games for Windows, and in 1992 it shipped with Windows 3.1 itself. From then on it was simply there, next to Solitaire, on office and home computers everywhere, quietly eating lunch breaks.

It changed clothes over the years. Windows Vista’s version offered a garden of flowers in place of the mines, for anyone who would rather not think about explosives on a coffee break. Windows 8 left it out of the box, and it became a free download from the Microsoft Store instead.

Then the mathematicians got involved. In 2000, Richard Kaye showed in The Mathematical Intelligencer that Minesweeper is NP-complete: deciding whether a board’s numbers fit any layout of mines at all is as hard as a whole family of famously hard problems. So if you find a quick method that works on every board, however big, you’ve settled P versus NP, one of the Clay Mathematics Institute’s million-dollar Millennium Prize Problems. No pressure. The Kid would settle for a marble.

The trouble with classic Minesweeper: the 50/50

Classic Minesweeper scatters its mines at random. Most of the time that’s fine. But every so often you reach a spot like this one:

Two covered squares, two 1s, and one mine between them. Both layouts fit every number. No amount of thinking helps: it’s a coin toss, and half the time the coin wins. Players call it a 50/50, and on a big Expert board one can end a run that was going beautifully. The board wasn’t hard. It was unfair.

That’s the itch no-guess Minesweeper scratches. A no-guess board (you’ll also see logic Minesweeper, or guaranteed-solvable Minesweeper) is checked before you see it, and kept only if logic alone can clear it. Mines, in Simon Tatham’s free puzzle collection, works this way. Puzzle books go one step further and print minesweeper as a pencil puzzle: every number is on the page from the start, and your job is to mark where the mines must be. Same numbers, no explosions, nothing left to luck.

Minesweeper strategy: what does each number still need?

Almost every Minesweeper move is one question asked of one number: how many mines does it still need, and how many places are left for them? Good players don’t really see a 3. They see a 3 with two flags beside it, which is a 1 with one job left. Hold on to that, and the rest of this section is the same question, asked cleverly.

The sure things

• A 0 clears its neighbors. No mine touches it, so every square around it is safe.
• No room to spare. If a number has exactly as many covered squares around it as mines still to find, they’re all mines. A 1 in a corner with one covered neighbor has found its mine.
• Full numbers. If a number already has all its flags, every other covered square around it is safe.
• Take away what you’ve found. A 4 touching three flags is really a 1 now. Many players call this reducing, and it turns scary numbers into easy ones.

Two numbers at once: the 1-1 and the 1-2

Patterns are just two or more numbers read together. They usually sit along a straight edge of covered squares, the wall where the open part of the board meets the unknown.

• The 1-1 from a wall. A 1 at the very end of the edge touches two covered squares, and the 1 beside it touches those two and one more. The first 1’s mine is in the pair they share, which gives the second 1 its mine too, so its third square is safe.
• The 1-2. Now make the second number a 2. It touches three covered squares, and two of them are shared with the 1, which can hold at most one mine. So the 2’s third square, the one the 1 can’t reach, must be a mine. This is the pattern you’ll use most.

The 1-2-1 and the 1-2-2-1

The two famous Minesweeper patterns are the 1-2 used twice, once from each side.

The 1-2-1. Three numbers, 1, 2 and 1, along a straight edge: the mines sit over the two 1s, and the square over the 2 is safe. Read the left 1 and the 2 as a 1-2, and the square over the right-hand 1 is a mine. Read the 2 and the right 1 as a 1-2 the other way, and the square over the left-hand 1 is a mine. That’s the 2’s two, so the square in the middle is clear.

The 1-2-2-1. Four numbers, 1, 2, 2 and 1: the mines sit over the two 2s, and everything else along that stretch is safe. The 1 and 2 on the left put a mine over the right-hand 2, and the 2 and 1 on the right put one over the left-hand 2. Each 1 now touches a mine, so each is full, and the squares at the ends are clear.

Once you know them you see them everywhere: on edges, in corners, turned on their side. They also hide in disguise. A 2-3-2 where each number already touches one flag is a 1-2-1 once you take the flags away.

Mine counting: the endgame

Near the end of a board, the total starts to matter. Classic Minesweeper’s counter shows the mines minus your flags, so you know how many are still out there. Say two are left, and two numbers far apart each still need one mine in places that don’t overlap. That accounts for both, so every other covered square is safe, even squares no number touches. Mine counting is how good players finish boards that look stuck, and in a no-guess puzzle the count is often the last key.

When the patterns run out: “what if”

Harder boards sometimes need one more move. Pick a covered square and suppose it’s a mine, then follow what that forces: this number is now full, so these squares are safe, so that number needs its mine over there. If you reach a number that can’t be satisfied, the supposition was wrong, and the square is safe. It’s Sherlock Holmes’s method from The Sign of the Four, more or less: rule out the impossible, and what remains must be true. It isn’t guessing, because you commit only when the logic says so, and in a fair puzzle the chain is short enough to follow in your head.

The Kid’s Treasure Map: a daily minesweeper puzzle, with treasure

Every good treasure hunt needs a map. Robert Louis Stevenson said Treasure Island grew out of a map of an island he drew with his stepson. Indiana Jones told a lecture hall that X never, ever marks the spot, and was proved wrong later in the same film. In the Fibbersons’ backyard, numbers mark the spot.

The Kid’s Treasure Map is our free daily minesweeper puzzle. The Kid buried treasure in the backyard and drew a map. Each dug square shows a number: how much treasure is buried in the 8 squares around it, corners too. Plant a flag on every treasure and he digs them all up. It plays like the pencil-puzzle kind of Minesweeper, with a few cozy changes:

• Every number is there from the start. You don’t uncover squares, you mark them: tap to plant a flag where treasure must be, or switch to Empty and ring a square you know is clear.
• Nothing explodes. A wrong flag never ends the game. A number with too many flags around it turns red with a +, and Back one takes your last move back.
• The map tells you the count. It says how many treasures are buried, and the count under it shows how many you’ve flagged, so treasure counting is built in.
• Some squares never hide anything. Puddles and the sandbox never hide treasure, and neither does a dug square.
• Numbers fade when they’re done. A number with all its flags goes faint, so your eye goes to what’s left.
• No guessing, ever. Every map has exactly one answer, and you can always reach it by logic.

A new map comes every day at midnight, your time, the same for everyone. Monday to Saturday it’s 8 × 8 squares, and Sunday’s is 8 across and 10 tall, with a little more buried. A map hides 9 to 13 treasures, and when the Kid digs them up you see what he buried: some mix of marbles, toy cars, brass keys, seashells, coins, buttons, dinosaurs, yo-yos, bottle caps and thimbles. A map takes about two minutes, and on a keyboard the arrow keys move, Enter plants a flag and O rings a square as empty.

How each map is made

Each day’s map is made from the date by a program, so everyone gets the same one. The maker buries the treasure, digs every other square, then covers dug squares back up one at a time. After each one, a solver works the map out from the numbers alone, the way a careful player does: one number at a time, then two side by side (the 1-2 and its cousins), then the count, and on harder days a short “what if”. A square stays covered only if the solver can still find every treasure. So a finished map has exactly one answer, and every pattern above works on it. How we make puzzles with exactly one answer has more on how the family’s dailies are checked.

Minesweeper for kids, and for anyone who flinches

Classic Minesweeper is a lot of things, but cozy isn’t one of them. The Treasure Map is gentle: there’s nothing to blow up and no way to lose, there are very few words, and your first map is a tiny 5 × 5 practice one that walks you to your first two treasures a step at a time. If you can count to eight, you can play. It’s the same logic as Expert Minesweeper, set in a backyard, which makes it a good one to share across a kitchen table: a kid reading the numbers, a grandparent spotting the 1-2-1.

Par, streaks and bragging rights

Every map has a par time, about what the fastest third of players take. Finish under par for a gold flag in your week. Your result shows your time, your streak and what the Kid dug up. Once the treasure is dug up it shows for a moment, then the yard goes back to plain grass, so a screenshot never gives the day’s map away, and Share sends only your map’s number and your time, with a link for a friend to try to beat it. The Kid’s Treasure Map also has its own board for your group and for the whole world, fastest first.

Tips for your first no-guess map

1. Start with the 0s. Every grass square touching a 0 is clear: ring them.
2. Then the tight spots. A number with exactly as many grass squares left as treasure still to find has treasure under all of them.
3. Ring as you go. Rings aren’t required, but each one takes a square off the list for every number nearby.
4. Look for the 1-2. It’s the move you’ll make most, and the 1-2-1 and 1-2-2-1 are built from it.
5. Count near the end. When you’re a treasure or two short, check which numbers still need one. The rest of the grass is often clear.
6. Stuck? Check your flags. A red number has too many, and Back one is right there.

For a square-by-square walk through the practice map, see our guide to minesweeper puzzles. If you like numbers that turn into something, Nonograms, and how Grandma’s Knitting knits them is about a puzzle where they draw a picture. And Hashi puzzles and Lacey’s Web is about one where they build bridges.

Where to play Minesweeper online, free

• Mines, in Simon Tatham’s free puzzle collection, plays in a web browser, with no-guess boards in any size you like.
• Microsoft Minesweeper is a free download from the Microsoft Store on Windows, for the classic look.
• The Kid’s Treasure Map is one no-guess map a day, free in your browser on a phone or a computer, with no download and no account.

Minesweeper has been teaching people to think before they click since the 1980s. We just like it better when the thing under the square is a marble.

Questions people ask