Wedge - four-space extension
![[Diagram]](../../diagrams/6/17427ba3a96958d169a21d17013b2354.png)
The four-space extension
An extension as far as
is interesting here, but provocative. Black may well invade.
![[Diagram]](../../diagrams/32/beb1a7436cbf50066afbd325a17ac410.png)
Perfect shape for White
Now White's stones are perfectly placed.
![[Diagram]](../../diagrams/40/3c0a12d6660693942cef6cfbea1cf7ab.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.