Why does Lichess only tell me my "inaccuracies", "mistakes", and "blunders", and not e.g. my "brilliancies"? A computer analysis of a game in Lichess lists your "inaccuracies", "mistakes", and "blunders".  An example is below:



What I don't understand is why Lichess doesn't point out my good moves.  It seems there is some inherent problem identifying strong moves, which is not present when pointing out poor moves.

Question: Why does Lichess only tell me my "inaccuracies", "mistakes", and "blunders", and not e.g. my "brilliancies"?
It's really hard to tell what a brilliancy is. For example, you might try to say that a brilliancy is a move that's much better than any other move on the board.  Well, if you offer me a queen exchange and I play queen takes queen, you taking back my queen is probably a much better move than any alternative, but it's definitely not a brilliancy. So maybe a brilliancy is a non-obvious move that's much better than any alternative. OK, but what's non-obvious? Maybe you could do something based on the depth you have to go in the search tree to prove that the move is good, but that probably still isn't right because a long sequence of exchanges is usually obvious but, by construction, goes deep into the tree. Or, suppose you trap my queen: by the proof depth metric, that would be a brilliancy if I can insert a long sequence of pointless checks before you take my queen, and a normal move if I can't.

In contrast, bad moves are easy to detect: if a move is suboptimal, you just compare its score against the score of the best move and use a more negative word for bigger differences.

Fundamentally, there's only one best move in any situation. As far as the computer is concerned, you either played it or you didn't.  Bad moves are bad moves, but brilliancies are good moves that most players wouldn't have seen, and that's as much a statement about "most players" as it is about "good moves".