InvincibleTheGamesOfShusaku/Game 37 analyzed with KataGo

Moves 15 to 16  

After caps, is the first move that strikes as strange. Of course the idea is to force White to play but the natural move would be at A.

is also the first commented move but Shuko explains why it is not at B. The natural move, which is also KataGo's suggestion, is not discussed.

KataGo peaceful  

In this peaceful variation, KataGo maintains a comfortable lead for Black.

KataGo aggressive variation  

In this variation, starting with attacking the white stones, both build influence. Black can aim at A at the bottom, White at Black's weakness B at the top.

Sacrifice  

can sacrifice two stones to take a position at the top. The aji at A is still there.

Moves 21 to 30  

After White's submissive response, Black gets the reinforcement at the top and White pincers the top right.

When attaches, Black doesn't respond locally but counterpincers at . Shuko says A would be dubious because it would lose sente. KataGo seems to agree but wouldn't pincer. Instead it prefers at (the hane at A can be played as a forcing move right before). This would indeed be thick. If White plays on the side, Black can return to the top. If White continues at the top, Black can take the side. Overall in the game looks like a bit of an overplay.

White on his turn leaves unanswered to take a big point at the bottom. Again, KataGo would again hane before tenuki.

Moves 31 to 40  

Since White has left the battlefield prematurely, KataGo would return to the hane of A. Instead Shusaku splits at , providing purpose to his marked pincer stone. KataGo evaluates this as a 3 point mistake. White's reinforcement at the top is logical but again a hane at A would be more natural: is probably too close to Black's solid three stones. is shapewise light but strategically heavy.

Now Shusaku turns to the bottom with . Instead KataGo suggests moving out his stone at B, taking advantage of White's loose shape.

Instead of another diagonal at , KataGo wants to force in the upper right before killing the aji at the top with G. Shuko calls solid and aiming at the cut at H.

We can see how AI gives high importance to the efficiency of existing stones while human pros were shifting back and forth between local thickness and developing empty area, probably thinking more about global efficiency.

Moves 41 to 50  

As if the game weren't complex enough already, makes another invasion, after having reinforced White with the - exchange. Black seems to deliberately create multiple targets to invite a White attack. All of that evades KataGo's attention, who is still focused on luring out the stone at A and unsettling White's top as a consequence.

Shuko calls solid but provides an alternative: leaning against the left side to attack the bottom on a large scale.

Shuko also praises the timing of Black's peep at .

Moves 51 to 60  

For the spectator it looks as if both are shadow boxing. doesn't attack, since is thick. is another thick move and White feels compelled to reinforce his big shapeless group with . Then Black moves out his other group. If we take into account the aji at the top, White's global position suddenly looks thin.

Moves 61 to 70  

Shuko calls the sequence up until "somewhat crude" and tries finding a justification (see next diagram). KataGo dislikes the empty triangle of in particular. It would cut at A instead, putting the pressure on white's group below and willing to give up the marked stones.

White forces with and before linking up his stones. KataGo wants to threaten the bottom on a large scale, with a thick move like A. This would bring the game around B+2.5

Shuko's diagram  

This is KataGo's response to Shuko's diagram. After Black connects at A, White jumps to B and Black actually has not so good shape. He needs C to live but that looks rather submissive. That's not the refutation Shuko gives for his own idea but it might be what Shusaku disliked.

Moves 71 to 80  

So when Black links up with and , the global thickness returns to Black. Shuko acknowledges as "the key point overall"

however is a bit weird, since White has already reinforced at . The analysis with KataGo is not easy, since it continuously wants to draw out that top stone, a maneuver that may have been underestimated by the pros. In any case, the invasion provides White with a last opportunity to make the game close. Shuko praises White's answer at which sets up a potential link underneath if needed.

Moves 81 to 90  

The opportunity is . Probably Shusaku's intention was to sacrifice the corner for outside thickness all along and weaken White's stones in the process. could have given Black what he may not have wished for:

Alternative for 84  

White can turn the tables of thickness by sacrificing the corner with . If Black prevents White from linking up with territory, is severe.

The crucial insight is that White can play A in sente against Black's corner, which makes available the peep at B. Suddenly Black is not as thick anymore.

With perfect play according to KataGo, Black will still come out victorious but this was at least an opportunity to stage an upset, should Black make a mistake in the ensuing fighting.

Due to Black's reinforcements, White's groups will have to live on their own and Black picks up the points in the process.