PlayingAProGameBackwardsGame1/Right side

3/4 point play  

Bill: After - (not played in the game), there is a 3/4 point play (miai value) in the marked region.

3/4 point play, Black first  

After - Black has 1 point ().

3/4 point play, White first  

After White has 1 point at , and Black has 1/2 point at . (Black can play - in sente.) The local count is -1/2.

In the disputed area the original local count is 1/4. Either player can gain 3/4 point in one net gote play.

Hanami ko  

The evaluation above depends upon White's not playing - in this diagram. If White does so Black can start a hanami ko with . In the game the - exchanges were made at the 1 point level. Since this is a hanami ko, White needs larger ko threats than Black. White has 3 large ko threats at and around z on the bottom. (I don't think the threat at y is quite large enough.) Black has ko threats at a, b, and c, and 4 threats at and around d, for 7 threats, 3 or 4 threats more than White. White should avoid the hanami ko, even though he takes first.

Curious sequence

Curious sequence  

Bill: Instead of taking his 1 point sente at a, Black played the 3/4 point play, - . Then instead of playing the 1 point reverse sente at a (or another 1 point play), White filled with , leaving Black with 1/2 point of territory at . How come?

Goodbye, eye  

at . at .

Bill: If White does play , Black can reply with - , taking away White's eye on the edge. Later White must make a protective play at .

However, White must protect at anyway. After the protective play at , the White stones to the left will still have only one liberty when all the dame are filled, obliging White to protect at . Black gains nothing by taking away the eye.

Did both players, who are obviously strong, made technically inferior plays on the right side. Did they both have the same blind spot about ?

Let me speculate. I think that both players had already read to the end of the game. White knew that he was going to get the play at a, anyway. In that case, why not preserve the eye? It might not help, but it couldn't hurt. As for Black, all other reasonable variations left White with the eye. If White protected the eye, as in the game, no harm done. If not, I don't know.... Black could fall into a trap if White plays elsewhere.