Tsumego
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Tsumego (詰碁?) is the Japanese term for a Go problem based on life-and-death. The term likely comes from tsumeshogi (詰将棋 tsumeshōgi?), as (詰める tsumeru?) means mating in Shogi but has no meaning in Go. Tsumego problems are common in newspaper columns; the usual format is of a position set up on some delimited area of the board, and the instruction reads something like 'Black to play and kill White'.
The form of the problem in fact goes back many hundreds of years; such problems are known in collections found in old Chinese books dating from about the 13th century. They were presumably composed and collected from actual games much earlier. They range from positions quite commonly occurring in games, which every strong player ought to be familiar with, to deliberately difficult puzzles. Some books of the latter type are still used for professional training.
A number of conventions are understood in the problems. Firstly, the task is to kill a group, or to prevent it being killed. There is no specified number of plays (as would be usual in a chess problem); in fact that makes less sense in go, because a killing or living play once found does not really have specific variations that follow (though there is sometimes a more interesting 'main line'). If part of the board only is shown, as is usually the case, the rest of the board can be assumed to be empty. Escape of the group under threat into an area not shown should not be relevant in a well-composed problem (this is one way in which such problems differ from real games). Seki is life, from the point of view of tsumego; on the other hand achieving ko for life or death is considered failure, unless the problem actually states this as objective. Other questions that might matter in a game, such as leaving the best situation in terms of ko threats, or later endgame plays, are ruled out of consideration.
