It is normal for machines of the type having multiple pay lines available, that the player would purchase the option of playing for a win on lines other than the centre line. In order to add further player interest, the game is also provided with a random feature whereby under certain circumstances, a further combination of symbol positions. referred to as the "mystery line", will be randomly selected by the machine's controller to give the player another winning opportunity. A prize is paid to the player in the event that a predetermined combination of symbols is displayed in the randomly selected arrangement of symbol locations, "mystery line".