Opening for analysis

[Bill Spight]

140: Why bother with K18? You can't kill his northern group now. M7 is huge.

142: You are ahead by a bunch. There is no need to allow him to create complications. Play B7. Then A7 and A8 are miai. This secures your big capture, and his chances on the west half of the board are exactly zero.

149: You are fortunate that he did not see A10 ( You can't play B7 - it puts you in atari ). Then he lives. This underscores the point about 142.

The problem is W144, which should be at B-07, capturing the A-07 stone.

[Joaz Banbeck]

The problem is W144, which should be at B-07, capturing the A-07 stone.

Yes, B7 works then too. It seems to be the vital point for the position.

For 140: Can I not kill? I thought 140 was sente, threatening H15? Can black live for sure if I get H15 after 140?

Ooops! You're right, it does kill.