As many cells as mines
When a number touches exactly as many hidden cells as it shows, every one of them is a mine.
A 3 with only three hidden cells around it has no choice: its three mines must be in those three cells. The same goes for a 2 with two hidden cells, or a 4 with four. Flag them, and the numbers around them often give you the next move.
How it works
Look at the highlighted number and count the hidden cells around it.
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, the only cells one number can prove belong to a number with as many hidden cells as mines and no flags around it.