is only one more rule to learn before you can begin playing. The concept
is illustrated in the figure above. Here a stone making a capture is
vulnerable to being recaptured immediately, which would repeat the original
position. This situation is called a ko, and a special rule prevents
the game from going on endlessly.
The rule is this: if Black captures as in Diagram 1, White may not recapture immediately but must wait at least one move to recapture. This can lead to tactical fights at other places on the board. If recapturing the ko is important, White will look to make a threatening move that must be answered, so he can come back and recapture the ko.
Diagram 2: White may not immediately recapture.
Diagram 3 Black has just captured the ko, and it is White's turn
to play. White responds by playing at 2 in Diagram 4, threatening
to take away the second eye from the Black group above.
In Diagram 5 Black defends his upper group by securing his second eye, and now White can return and recapture the ko in Diagram 6.
Ko positions may also occur on the edge of the board, as in Diagram 7, or in the corner as in Diagram 8. In each case Black may start the ko fight by capturing.