The board is three squares by three and there is one mine on it. Clear it and you have won a game of minesweeper in about four seconds, which is the point: the win is a currency. So are the cells you uncovered. There is a tutorial for anyone who has never played, and a skip button for everyone who has.
Wins and cells buy hints, then a wider board, then more mines to make the wider board worth clearing, then the machinery that starts clearing squares for you. The difficulty curve is yours to set, because every purchase is a choice between a board you can beat quickly and a board that pays properly. What began as a four second puzzle ends up as a grid you supervise rather than solve.