Wedge - four-space extension
![[Diagram]](../../diagrams/27/912831f1521c2642512dd3a3a071f48f.png)
The four-space extension
An extension as far as
is interesting here, but provocative. Black may well invade.
![[Diagram]](../../diagrams/21/5800dc571d3bfef33304bb3df18f45cd.png)
Perfect shape for White
Now White's stones are perfectly placed.
![[Diagram]](../../diagrams/2/89dc99a059376893152a045cc217d6bc.png)
Black invades
Therefore it is natural enough for Black to invade, and try to make the marked white stone into a target for attack.
as shown is popular in pro games: a is also seen, while b was played in older games.