Starting from an ocean of squares with unknown contents you must mark all the squares with mines and reveal all the clear squares. You don't actually have to mark the squares with mines, but it is a lot easier if you do. Once you have cleared all the un-mined squares, any remaining mined squares will be marked for you.

If you left click on a mine, or auto-clear a square with a mine in it you lose. To help prevent accidents, you aren't allowed to auto-clear around a square unless the number of marked mines equals the number given in the square.

By choosing Settings ▸ Preferences from the menu you can change the size of the games. Larger sizes obviously take longer and require more concentration. Smaller games are more frantic. We provide Small, Medium, Large and Custom sizes.

Figure 4 The preferences dialog.

On the right hand side of the dialog there are three parameters for controlling the custom size. Horizontal and Vertical are the width and height of the desired grid in squares. The number of mines is - obviously - the number of mines you need to find. If this number is set too high or too low then the game becomes very easy. The number of mines is limited to slightly less than the total number of squares.

There is a check-box in the properties dialog entitled Use "I'm not sure" flags. If you enable this then, when right-clicking on a square, it cycles between the normal flags used to mark the square as mined, a flag with a question mark on it and no flag. This new flag is to help you with your reasoning, to mark mines you think might be a mine but aren't sure about. These flags have no effect on the game; you still have to use the appropriate number of red marker flags to be able to clear around a numbered square.

Figure 5 The sequence of flags when "I'm not sure" flags are enabled.

The other check-box in the properties dialog is entitled Use "Too many flags" warning. This feature will show you a warning when you have placed too many flags. This is disabled by default, as it provides so much hint that it could be considered "cheating".

If you get stuck - it is reasonably common to end up with two options that you can't logically resolve - then you can either guess, or ask for a hint. When you choose Hint from the Game menu a single square is revealed (plus surrounding squares if it is blank). The choice of square is random, but should be helpful. There is 10 second penalty added to your time whenever you use a hint.

If your score is in the top ten you will be shown the list of top scores and have an opportunity to change the name recorded in the high score table. You can also review the scores later by choosing Scores from the Game menu. The drop-down menu at the top of the dialog lets you look at the scores for other board sizes.

Figure 6 The high scores dialog.

Resizing the window makes the squares bigger or smaller to suit. If you want to make maximum use of the screen then there is a Fullscreen option under the Settings menu. You can also use the F11 key to toggle full-screen mode.

The game can be paused automatically when you start using another window, or paused by choosing Pause from the Game menu. The playing area is blanked so you can't think ahead while the clock is stopped. To start playing again press the button labelled "Press to Resume".

These are a few basic situations which should be incredibly obvious, but if you're struggling with how to play the game, they should be useful. The first case is where you have an isolated covered square and most of the squares around it read 1. That covered square is a mine.

Figure 7 The simplest case.

The next simplest case is where you have two covered squares adjacent to each other and both squares on one side are marked with a 2. If they have no other uncleared neighbors, then both squares are mines.

Figure 8 The two mine case.

Finally, when there are three uncovered squares in a row and the clear square beside the middle one is a 3 (once again this square should have no other neighbors) then all three are mines.

Figure 9 The three mine case.

These are the simplest cases. Other permutations on these simple situations are possible, for example the three squares in the previous example could be in an L shape.

Simple analysis will solve most of the puzzle, but not all. Before going on to the next sections, where we give you more advanced hints, you should play for a bit and see what you can work out for yourself.

These are some more complicated situations. They are a bit of a step up from the last section, so we hope you took our advice and played for a bit first.

In the example below the mines are to the left of the ones. We figure this out by a process of elimination. If the square to the left of the 2 was a mine then the 1s would both have their maximum number of mines leaving no free square for the second mine adjacent to the 2 (since they would also be adjacent to the 1s). Having eliminated the middle square we are left with two squares we require for the 2 so they are both mined.

Figure 10 A not-so-obvious pattern.

This situation can be disguised, for example consider the figure below. It is the same situation, but the extra mined square on the right has increased all the numbers by 1.

Figure 11 The extra mine disguises a copy of the previous example.

Now we're going to try a complicated example. It illustrates two points. The first is that even if you aren't sure which squares are mined, restricting the possibilities is helpful. The second is that knowing which squares aren't mined is nearly as good as knowing which are mined.

Assume that, in the figure below, we start off knowing that the top left square is mined and so the two squares marked 2 on the left only require one more mine. Next observe that the left-most 2 implies that one of the covered squares beneath it is mined, but we don't yet know which one. Since at least one of these squares is mined and they are both neighbors of the second 2 then we know that that 2 is also satisfied by one of these two squares (we still don't know which one). This means that the square beneath the 4 is clear because it is also a neighbor of the second 2 and not one of the two squares we identified previously. This one blank square now leaves the 4 with only four neighbors - all of which must be mines. Not only does it tell us which mines surround the 4, it now tells us which of the squares beside the 2 is mined!

Figure 12 As tricky as it gets.

This sort of situation is tricky. In all the other examples you can learn to look for patterns and avoid thinking hard. Situations like the one in the figure don't crop up easily or in easily recognisable places. Often it is easier to just ignore them and keep playing elsewhere in the hope that you can start clearing the squares from the other side.

Remember, the edge of the board is just the same as a large cleared area (but without the numbers). Often working at the edge of the board is the easiest way forward.

Sometimes you end up in a situation where there is no way to deduce what the configuration is. In these cases you either have to guess or use the hint function (Game ▸ Hint). Sometimes it isn't a 50/50 situation and instead of taking a hint you might like to gamble on the most likely outcome.

One final hint: remember the counter on the bottom left of the window that tells you how many mines you have left? Often, near the end of the game, this number can help you figure out what possible places mines can be. How to do this is up to you to figure out.