Surprise Moyo

White reaction  

Charles Matthews This seems reasonable for White, though Black is now more likely to get the endgame play at a in sente. Where did Black play now? White has built good central thickness, but in gote. If Black spends time making a capture of the marked white stone on a small scale, 'forcing' White at a, that's quite poor play (next diagram assumes this).

White reduces?  

Charles Hey, anyone can build a moyo with enough help from the opponent. Black at b instead of the endgame sequence in the lower left would have been appropriate.

After White invades, White c not at 3 is expected to make a troublesome ko. White 5 and 7 do show good vision here.

The normal technique from pro games would be White starting at d, a reduction play that aims at the invasion point White 1.

White reduces?  

Surprise moyos are not so surprising if you get surprise extra moves: where does the marked stone come from ? I mean: you left out sequences where Black's major strategic error has occurred.Dieter

Charles Yes, it seems that Black has again chosen to capture the marked white stone, on a small scale. So Black has a problem with the small moves mistake.

Jasonred Could it be that Black made a not ambitious enough attempt to gain the right side, with White capitalising? That seems more plausible than using five moves just to capture one stone...