Sesmaa's Go Mistakes

A.K.A. My DaveBase
Game 3: Sesmaa (20k) [B] vs Bonga (19k) [W]

Mistake 3

Or how to lose 87 points in one move:
Chasing after 3 settled White stones and ignoring life and death analysis gives White sufficient advantage to turn the game around for the win.

(Alternatives in blue/green)


Game 2: Sesmaa (20k) [B] vs 9romit (6k) [W]

Mistake 2.2

Failure to recognize mistake 2.1 and the weak stone at O18 leads to further loss:
when White cuts into Black's group with R16, stretching from O18 to N18 does little to help Black's position.

Alternative 2.21

R15 is most effective: (thank you Raylu)
atari to White's R16 guarantees life for Black's group and directs the flow to the right side of the board.

Alternative 2.2

S16 is a proper response, setting off a capturing race to Black's advantage with atari to White's R16 supported by Black's R14.
Once Black group is settled,
nobi at N18 is considerable, but tennuki looks like the bigger move.

Mistake 2.1

What develops as a
joseki sequence in upper right corner, becomes unfavorable when Black plays a bad move at O18:
This mistake is evident once compared to the similar sequence on lower right corner:

Alternative 2.1

For this
joseki, Black may opt for the cut threat at N18, or even a hane at O15.
However, considering the rest of the board, 9romit suggests
tennuki: a small knight's jump at F17 maintains sente and decides the direction of play while settling the third corner.


Game 1: Sesmaa (20k) [B] vs Bugcat (9k) [W]

Mistake 1.1
Starting with a low one-space approach to white's komoku on D17, I respond to white's kick with a small knight's jump in an attempt to extend towards the middle left of the board:

Three moves later the toll becomes evident:

Alternative 1.1
Instead -as per bugcat's suggestion- a stretch or nobi creates a solid wall and protects the black stone at C15 against a painful hane.

If White then extends with a one-space jump, Black can fix the weakness at D7, and once White extends at the bottom, *then* attempt a three-space extension on the fourth line, securing the left side of the board and effectively using both walls:

Mistake 1.0
"Connection is important, even if there is a ko" -bugcat

This sequence begins even before mistake 1.1 takes place and only becomes fully evident for black until afterwards:

With move 16 at E3, Black ignores the
atari created by White's B7 on move 15, accepting E7 as the response to White's capture of C7.
Once White follows with a
hane to E3, Black has 5 weak stones attached to White's secured corner.

Alternative 1.0
Immediate response to White's atari on Black's C7 not only connects, but threatens to follow up with B8. This forces White to fix at C9, after which Black can attach to White's D3 with E3, and later respond to White's hane by threatening to cut at C3 with D4. Once White fixes at D2, Black can stretch to F3, creating a net in the process and confining white to the second line.