Clear the board without detonating a mine. Numbers tell you how many mines are hiding in the 8 tiles touching that number — use them to work out which tiles are safe.
Reveal: left click (desktop) or tap (mobile) a tile.
Flag: right click (desktop) or press and hold ~half a second (mobile) to mark a suspected mine.
Win: reveal every safe tile. Your best time per difficulty is saved automatically.
Your very first click is always safe — mines are placed only after you reveal a tile.