Checking the score fluctuations of the AI review during that corner exchange, you can identify which moves are good and which are bad (but take into account that the low level AI review has a margin of error):
- a move that loses 0 - 0.5 points is a good move.
- a move that loses 1 - 2 points is not a great move, but probably still acceptable for intermediate players.
- losing 3+ points with 1 move should probably be considered a mistake, also for intermediate players.
We can also categorize moves into tiers, for example:
- S tier = better than 0.5 points loss
- A tier = 0.5 - 1.0 points loss
- B tier = 1.1 - 2.0 points loss
- C tier = 2.1 - 3.0 points loss
- D tier = 3.1 - 4.0 points loss
- E tier = 4.1 - 5.0 points loss
- F tier = worse than 5 points loss
(move 3) The sequence starts with white’s approach at C14, which is good (S tier, losing 0.1 points).
(move 4) Black’s response at F16 is good (A tier, losing 0.6 points).
(move 5) White’s invasion at C17 is good (A tier, losing 1.0 points)
(move 6) Black’s split at C16 is good (S tier, losing 0.3 points)
(move 7) White’s push at D17 is a mistake (E tier, losing 4.4 points), B16 would be good
(move 8) Black’s block at E17 is perfect (S tier, losing 0 points)
(move 9) White’s hane at E18 is acceptable (B tier, losing 1.8 points)
(move 10) Black’s block at F18 is good (S tier, losing 0.3 points)
(move 11) White’s descent at E19 is acceptable (B tier, losing 1.8 points)
(move 12) Black’s block at F19 is good (A tier, losing 0.6 points)
(move 13) White’s tiger’s mouth at C18 is perfect (S tier, gaining 0.6 points)
(move 14) Black’s hane at B17 is good (S tier, losing 0.1 points)
(move 15) White’s block at B18 is perfect (S tier, losing 0.0 points)
(move 16) Black’s atari at D19 is a mistake (D tier, losing 4.0 points), B16 would be good
(move 17) White’s connection at D18 is a mistake (D tier, losing 3.8 points), B16 would be good
(move 18) Black’s connection at B16 is good (A tier, losing 0.8 points)
(move 19) White’s descent at A18 is perfect (S tier, gaining 0.2 points)
(move 20) Black’s block at A17 is a blunder (F tier, losing 11.8 points), tenuki would be good
(move 21) White’s capture at C19 is a blunder (F tier, losing 13.4 points), tenuki would be good
Many of the mistakes (in bold) cancel out, but overall black gained 8 points from move 3 until move 21. So it was a success for black.
Note that at no point in the sequence black had a chance to kill white.
Also note that the biggest mistakes were towards the end of the sequence, when both players kept playing here while they could have played elsewhere. As nothing bad seems to happen from it, such mistakes may go unnoticed, but with just a couple of such missed opportunities to take/keep sente, you lose as many points as when you let a group die. Spotting such opportunities may be the lowest hanging fruit with the greatest rewards when it comes to improving your results. For each time you manage to avoid such a mistake, your level of play over the whole game increases by as much as a full rank.
