Reveal a cell with a tap or left-click. Numbers show how many mines touch that cell. Opening a blank cell clears the whole region.
Flag a suspected mine: long-press, right-click, or switch on Flag mode below the board so every tap places a flag (long-press then reveals).
Chord: tap a revealed number that already has enough flags around it to open the rest. Clear every safe cell to win. Your first tap is always safe.