The 1-2 pattern
When a 1 and a 2 stand side by side along hidden cells, the 2 shows you a mine and the 1 a safe cell.
One number alone tells you nothing here: the 1 has three hidden cells and one mine, the 2 has three hidden cells and two mines. Together, they tell you two cells for sure. You will meet this pattern in almost every game.
How it works
A 1 and a 2 stand side by side. The 1 touches three hidden cells, the 2 touches three too, and two of them are the same (yellow).
Your turn
Each board is a real position from a game. Tap or click to open; right-click, long-press or switch on Flag to place a flag. If you are not sure, take a hint: the first one only shows where to look.
Which hidden cells can you be sure of?
How the exercises were chosen
A computer checked every board: in what you see, no number on its own proves anything, and comparing two numbers proves exactly the two cells of the 1-2 pattern. So the exercise cannot be done with the earlier lessons, and it does not need anything harder.