Mah-Jong is a Chinese game played by four players, using pieces called "tiles". All tiles come in pairs, and the aim of the game is to gather as many pairs as possible; however, two tiles forming a pair can only be gathered if they are free, i.e. if either their left or right edge isn't against another tile. A tile that is placed between two other tiles can therefore not be clicked. Each player plays with his own tile stack. To win the Mah-Jong challenge, you must draw pairs of tiles to obtain the highest score. If you run out of solutions during the game, you can shuffle the tiles, but that will cost you a few points.