The 1-2 Pattern

This lesson will explain what to do when you see a 1-2 pattern like this: [You must have a graphics browser]

Note that it does not matter what is to the left of the 1 or to the right of the 2.
Also note that this can always be used for the equivalent of a 1-2 pattern as well.

You can see that the 1 is only touching the three squares as shown: [You must have a graphics browser]
and the 2 is also only touching three squares: [You must have a graphics browser]
The 1 and 2 share the following two squares: [You must have a graphics browser]

Since there must only be one bomb in the shared squares (they are touching the 1), the 2 needs one more bomb touching it. As you can see, there is only one square left, which can safely be marked as a bomb: [You must have a graphics browser]


This can be extended to several useful situations:

In [You must have a graphics browser], application of this rule on both the 1-2 and the 2-1 shows that there is one bomb under each 1 : [You must have a graphics browser]

In [You must have a graphics browser], this rule shows that the two bombs are under each of the 2s : [You must have a graphics browser]


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