Clear every square that isn't a mine. The numbers tell you how many mines touch that square — the rest is deduction. Your first tap is always safe.
Tap a square to uncover it. The first tap can never be a mine.
A number says how many of the eight surrounding squares hold a mine.
Long-press, or turn on Flag mode, to mark a square you are sure about.
Clear a square touching no mines and the whole area opens at once.
A 1 beside one unopened square means that square is the mine.
Clear every safe square. Your quickest time per level is kept here.