Hard logic puzzles

Every number is given and nothing new opens. Find every mine — and you cannot get going with one or two numbers alone.

These puzzles are for players who find ordinary Minesweeper too easy. If you have only just started, go through the Tutorial first and play a few games on the regular sizes.

Mark a cell safe with a dot, a mine with a flag. When there are as many flags as mines, press Check: if every mark is right, the puzzle is solved; if not — Boom!, and the board starts again from scratch. There are no hints and no solutions to look up.

How these puzzles are made

A computer starts from a full board, where every safe cell shows its number, and takes numbers away one by one while the solution stays unique. The numbers left are the ones you get. Then it searches for the version where no step is easy: whenever everything that follows from the last breakthrough is marked, the next mine or safe cell needs at least three numbers looked at together, the whole border at once, or the mine counter together with the numbers. The site's ordinary games never need such steps.

Each size has puzzles of two kinds. Compared with many other puzzles of their size, the hard ones are in the upper half, the very hard ones in the top fifth.

• Hard: about half of the moves need three numbers or more.
• Very hard: more than half of the moves need three numbers or more, and the first easy one comes late.

The steps these puzzles need are explained in the lessons Three numbers together, The whole border at once and Counting mines.