Go opening theory

In the game of Go, opening theory is the strategy of where, why, in what order, and in what shapes the first several moves are played. The middle game typically begins once the basic foundational areas called frameworks are established and "fighting" begins.

The opening is conceptually and traditionally divided for study into the sequences that are whole board openings and those that are corner openings. Each type constitutes a series of plays which have been studied for their balance (with the other) as well as for countermoves.

For a standard board, the most basic single concept for the opening is that plays in the corners are more efficient for making territory than plays on the sides or in the center.

Opening theory is less dominant in terms of study, for those wanting to reach a good amateur level, than in chess or shogi. It is, however, an important component of Go knowledge, though there is no single, codified source for it.

The standard sequences for the joseki in many cases come to a definite end, after which both players should move elsewhere. In some cases a sharp local struggle breaks out, which neither player should neglect. For those cases, the result of the opening may develop out of a 10×10 corner area into the rest of the board. Analysis without taking into account what other stones are in place then becomes somewhat meaningless. The longest 'book' corner openings are about 50-ply.

Most corner openings do not have special or picturesque names. A few that do are known by Japanese names: the taisha, the nadare (avalanche), the Magic sword of Muramasa. These are among the most complex, and are contraindicated for novices.

Because each early move is typically isolated, and neither forced nor forcing, patterns for play on the whole board have seen much less systematic study than for joseki, which in contrast often involve contact plays which require specific and immediate responses. Hence a game of Go may easily explore an unfamiliar path.

Only a relatively small proportion of openings have a recognised name. These include the Three stars opening (sanrensei), Two stars opening (nirensei), "Pinwheel" or Shusaku opening and Chinese opening (Chinese fuseki). To be more precise, these are names for the moyo (framework) formations which Black makes on one side of the board. Since White has a choice of perhaps two dozen legitimate variations on the other side, these are in fact large complexes of openings.

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Wikipedia