"Brilliant (!!) moves and Great Moves are always the best or nearly best move in the position, but are also special in some way.
We replaced the old Brilliant algorithm with a simpler definition: a Brilliant move is when you find a good piece sacrifice.
There are some other conditions, like you should not be in a bad position after a Brilliant move and you should not be completely winning even if you had not found the move. Also, we are more generous in defining a piece sacrifice for newer players, compared with those who are higher rated.
Great Move is a new move classification that is denoted by a single exclam (!). These are moves that were critical to the outcome of the game, such as going from losing to equal, equal to winning, or finding the only good move in a position. Similar to Brilliant moves, we are more generous on what we call a Great Move for new players compared with high-rated players."
[Event "nikkolafan vs. bakakuun"]
[Site "Chess.com"]
[Date "2023-03-04"]
[White "nikkolafan"]
[Black "bakakuun"]
[Result "0-1"]
[WhiteElo "534"]
[BlackElo "511"]
[TimeControl "standard"]
[Termination "bakakuun won by resignation"]
1. e4 e5 2. Nf3 d6 3. Bc4 f6 4. Nc3 Nc6 5. b3 Qe7 6. Ba3 Bg4 7. Be2 f5 8. Nd5
Qe6 9. Bc4 fxe4 10. Nxc7+ Kd8 11. Nxe6+ Ke7 12. Nxf8 exf3 13. Ne6 fxg2 14. Bxd6+
Kxd6 15. f3 gxh1=Q+ 16. Ke2 Qxf3+ 17. Ke1 Qh1+ 18. Bf1 Bxd1 19. Rxd1 Qxh2 20.
Ng5 Rf8 0-1