Gameplay mechanics were altered radically from the first two entries into the Pac-Man series - instead of eating dots, the player is required to eat keys in order to open doors, which open up sections of the maze that contain what in earlier games were known as "fruits" (foods such as apples and bananas, or other prizes such as Galaxian flagships), which are now the basic items that must be cleared. Once all the food is eaten, the player advances to the next level. (wikipedia.org)