The rules, very easy, are in stark contrast with the abyssal depths which can be found when analyzing a game. Such unexpected complexity is found among minimal rules and game materials of seemingly total simplicity.
The game of Go was created in Asia in ancient times. The first archaeological evidence goes back 4000 years (this age dates the pawns found in burial-places of nomad populations in Siberia) but the game has been diffused in Tibet, China, and Korea.
Confucius and Mencius talked about it, defining it a classic game, already in the 5th century B.C.

A monthly magazine, the Deutsche Gozeitung, was published in Gratz in 1909. The game spread later to the United States and to the rest of the world.
In Japan the national federation (Nihon Ki-in) has several millions of members and numerous tournaments reserved to professionals; the game moves economical interests more than any sport except for baseball and sumo.
The strongest players in the world are now the Koreans, who have recently pushed the development of the game to surprising levels, but a considerable number of strong players can be found in China. The game is played at a professional level also in a very limited number of Western countries. There is abundant specialized literature.
The game is played with apparently simple equipment. The checkerboard is traditionally built in a whole block of valuable wood; its size is 40x45 centimetres, it is slightly rectangular to compensate the perspective deformation; on its surface there is a grid of 19x19 lines.
The thickness of the necessary wood traditionally varies from 10 to 25 centimetres. To get such a thickness it is necessary to extract a whole block of wood from trees which are 500 to 700 years old. The wood, of clear colour and wonderfully streaked by numerous and parallel lines, can be of various species, but the most valuable is obtained from the Torreya Nucifera, “Kaya” in Japanese.
Magnificent masterpieces in lacquer and ebony were used in the past; they were richly decorated, and on them precious stones were used in the place of pawns; sometimes the white pawns were in valuable ivory and the black ones in jade (notice the tendency to use animal and mineral materials on a vegetable checkerboard).

Nowadays the pawns are obtained from black stone and valuable seashells, though scarcer and scarcer.
The cost of this material is the cause of today’s prevailing use of synthetic jade (not cheap, in fact) and glass, which is a material perfect for its weight, low cost and wide availability, but very fragile. Plastic is sometimes used, but it is not very appropriate and therefore the pieces are often weighted with invisible metal inserts.
These surrogates are now common because of the impossibility to use the traditional set for people who are accustomed to play on high tables and chairs, in contrast with the classic tatami and mats on the floor.

The pawns are kept in elegant rounded bowls in valuable wood, called go-ke. These bowls follow the same aesthetical considerations as mentioned for the goban (checkerboards) and the stones; bowls in rare and expensive wood are used; this didn’t stop the spreading of simple bowls in “profane” plastic.
A peculiar characteristic of Go is that it is considered a martial art and it has the same ranking system.
One level, or kyu, is equivalent to a handicap stone; a game can be played also between players with very different levels and skills, positioning a certain number of stones on the checkerboard before the game starts, at the advantage of the weaker player.
The difference in the ranking is equal to the number of handicap stones necessary to play a balanced game.

The game is played in turns, on a checkerboard (goban) of 321 intersections (19x19 lines), placing one stone at a time on a free intersection. Each stone, when placed on the goban, has four liberties or intersections directly adjacent; a stone survives until it has at least one liberty (an adjacent intersection not occupied by a stone).
The stones, once played, cannot be moved; they can be placed anywhere on the checkerboard except for the intersections where they would have no liberties (suicide position).
The stone or group of stones having all their liberties occupied by the adversary (completely surrounded) are lost and given to the adversary (they are prisoners). The purpose of the game is to surround the highest possible number of intersections (territory) out of the initial 361.