Mines
<p>
Try to expose every square in the grid that is not one of the hidden
mines, without opening any square that is a mine.
<p>
Click in a square to open it. Every opened square is marked with
the number of mines in the surrounding 8 squares, if there are any;
if not, all the surrounding squares are automatically opened.
<p>
Right-click in a square to mark it with a flag if you think it is a
mine. If a numbered square has exactly the right number of flags
around it, you can click in it to open all the squares around it
that are not flagged.
<p>
The first square you open is guaranteed to be safe, and (by default)
you are guaranteed to be able to solve the whole grid by deduction
rather than guesswork. (Deductions may require you to think about
the total number of mines.)