About Approach-Move Liberties (2009)
Liberties
Consider the first diagram, Black has an eye () in the corner. To capture the Black stones, White must play on last, and must play on all the points , and , before that. The points are direct liberties, while the points are approach-move liberties, which must be played before the matched -liberties. | |
In the second diagram, White still has to play all the -points. However, now White does not need to play the last (potential) approach-move liberty . Obviously, White still has to play the other two -points. From this diagram, we can see that, if we have just one / pair, then they are equivalent to only one real liberty. We can also see that, for every other / pair that we add, we get two more real liberties - both the , and the , have to be played. | |
By comparing both diagrams, we can see that the addition of an eye, not only adds a liberty in the eye itself (), but also promotes the (last) potential approach-move liberty (a ) into a real one (an ), thus gaining a real (approach-move) liberty for Black. | |