It's about time we had more than a near-exact clone of the classic Windows game, Minesweeper.
Left click: Reveal a box. Clicking on a mine will lose the game.
Right click: Change a box to either unmarked, flagged as a mine, or a question mark.
Middle click: Sonar ping which reveals all mines in a 3x3 square without the danger of setting them off. It comes with a 20 second cost added to your time. Left clicking while holding down the Alt key will also will do this.
Click with both buttons: If the tile is a number and the appropriate number of mines around it have been flagged, it will clear all the other squares around the number. Of course, if you've made a mistake, you'll probably set off a mine. Left clicking while holding down the Shift key will also do this.