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Rules: a number counts the mines in its eight neighbours

The number on an opened cell is how many mines sit in the eight cells around it (five on an edge, three in a corner). Uncover a mine and the round is over; open every safe cell and you win. Flags are only reminders, so flagging every mine does not by itself finish the board.

A cell with zero mines around it shows as blank and automatically opens its neighbours. That cascade is why a single click can sometimes reveal a large empty area.

Difficulty follows the classic sizes: Beginner is 9×9 with 10 mines, Intermediate 16×16 with 40, and Expert 30×16 with 99. On Expert roughly one cell in five hides a mine, so the same numbers demand much tighter reasoning.

Controls: you can finish without a right mouse button

• Open a cell: left-click, or tap while in open mode on mobile.
• Flag: right-click (again for a question mark, again to clear). On mobile, tap in flag mode or long-press for 0.4 seconds.
• Chord (open all neighbours): left-click an opened number, or press both buttons together.
• Keyboard only: arrow keys to move, Space or Enter to open, F to flag, C to chord, R for a new board.
• Zoom large boards with the + / − buttons or a two-finger pinch, and drag to pan.

Strategy: certain cells first, guesses last

Two deductions do most of the work. If a number equals the count of closed cells around it, all of those cells are mines. If a number is already surrounded by that many flags, every other closed neighbour is safe. Most boards fall to these two rules applied over and over.

Along walls you will keep meeting shapes such as 1-2-1 and 1-2-2-1. In 1-2-1 the cells facing the two 1s are mines and the middle is safe; in 1-2-2-1 the cells facing the two 2s are mines. Once these shapes are memorised your hand moves before you finish counting.

Reach for probability only when nothing is certain. Even then, prefer the cell that will reveal the most new information, often one in a wide unknown region in the middle, rather than a random edge. If you want a contest of pure skill, try the No-Guess Weekly. Certified weeks have been checked by a solver to be solvable from start to finish by logic alone.

History: the office game that taught the mouse

Grid games about deducing hidden mines from numbers appeared on several computers in the 1980s, but the version that fixed today's form was Microsoft Minesweeper by Robert Donner and Curt Johnson. It first shipped in the Windows Entertainment Pack in 1990 and became a built-in accessory from Windows 3.1 in 1992, landing on office PCs everywhere.

Many people were still new to the mouse at the time, and it is often said that a game demanding precise left and right clicks doubled as practice. The board sizes and mine counts for the three levels were set in that era and remain the standard today.

Minesweeper is famous in computer science as well. In 2000 the mathematician Richard Kaye showed that deciding whether a given arrangement of numbers is consistent is NP-complete. Put simply, as boards grow, finding a guaranteed fast method to solve them belongs to a class of problems believed to be fundamentally hard.

Questions about Minesweeper difficulty and opening moves

Where is the best place for the first click?

QuizLab never places a mine on the first cell you click or on any of its eight neighbours. That means the first cell always shows zero and opens a cascade wherever you click. Clicking in the middle spreads information in every direction and makes the next move easier to choose; clicking a corner opens less ground but exposes wall patterns early.

How big is the gap between Intermediate and Expert?

By mine density, Beginner is about 12%, Intermediate about 16% and Expert about 21%. The percentages look close, but as density rises the number of cells that cannot be settled by logic grows sharply, so on Expert a forced guess comes up far more often.

When should I use the question mark?

Use it to mark a cell you suspect but are not yet sure about. Unlike a flag it does not count against the remaining-mine counter, so it is handy for parking a hypothesis while you work on another part of the board.