Intermediate Minesweeper

Minesweeper is played on a grid of covered squares. Some of them hide mines; the rest are safe. The goal is to uncover every safe square without opening a mine.

Intermediate is a 16 by 16 grid with 40 mines, about one square in six.

• Open a square to see what is under it. A mine ends the game.
• A safe square shows a number: how many of its eight neighbours (sideways and diagonally) hold a mine. A square with no mine around it opens its neighbours for you, so whole areas clear at once.
• Put a flag on a square you know is a mine. Flags are only notes for you; they don't count toward winning.
• The game is won when every square without a mine is open. The counter above the board shows the mines minus the flags you have placed.

On a straight edge of open numbers, a few patterns come up all the time. Learning them saves you from working out each square from scratch.

• 1-1 from a wall: two 1s side by side at the edge of the board (or against open squares). The first 1's mine is in the two squares they share, so the square beyond the second 1 is safe.
• 1-2 from a wall: the 2 needs one more mine than the 1 can give it, so the square the 2 sees and the 1 doesn't is a mine.
• 1-2-1 along an edge: the mines are under the two 1s and the square under the 2 is safe.
• 1-2-2-1 along an edge: the mines are under the two 2s; the squares under the 1s are safe.

When no number is settled on its own, look at two numbers that share covered squares. If every mine one of them needs has to sit in the shared squares, its other covered neighbours are safe. If the shared squares can't hold enough mines for the other one, the rest of its neighbours are mines.

Work around the whole border of the open area before you decide you are stuck. A pair of numbers on the far side often opens the way back.

Click or tap a square to open it. Right-click, or press and hold on a phone, to put a flag on it or take it off. Flag mode below the board makes every tap a flag, which is easier on a small screen.

Tap a number whose mines are all flagged to open every other square around it at once (this is called chording). If one of your flags is wrong, that opens a mine, so flag with care.

Your first click is always safe. Each board starts at a cell marked with a gold ring: wherever you click first, that area opens, and from there the whole board can be solved by reasoning. Hint shows the next sure square and why; press it again to open or flag it. On a keyboard, the arrow keys move, Enter or Space opens, and F places a flag. Your game is saved in this browser.

Your fastest time on each level is kept on this device. Speed comes from reading patterns at a glance and from chording: flag a mine, then tap the number to open the rest of its neighbours instead of opening each one.

Use as few flags as you need. Flagging every mine costs clicks; flag the ones that help you chord.