The player must line up falling blocks of animals and foodstuffs. When an animal is aligned adjacent to a tile of its favoured food, the animal eats the food. Larger groups of connected food of the same type scores higher when eaten.
The favored food for each animal is as follows:
Dog-Bone Rabbit-Carrot Panda-Bamboo Monkey-Banana Mouse-Cheese
The default number of animal types in the game is 4. A game setting allows a fifth animal type, the Mouse.
Source: Wikipedia, "Baku baku", available under the CC-BY-SA License.