What is a brilliant move you recently got?

Brilliant Moves are always the best or nearly best move in the position, but they 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 additional conditions:

• You should not be in a bad position after a Brilliant move

• You should not be completely winning even if you hadn't found the move.

We are also more generous in defining a piece sacrifice for newer players compared to those who are higher-rated.

https://support.chess.com/en/articles/8572705-how-are-moves-classified-what-is-a-blunder-or-brilliant-etc

So for your move hxg4, you opponent had missed a chance to trap your queen with Bg3.on his last move. (Nc7 attacks your rook but Bg3 would have attacked your queen, which had no way to escape.)

By playing hxg4, you were giving your queen retreat squares if your opponent played Bg3 on his next move..

Your move counted as a sacrifice because you left your rook on a8 en prix. (liable to be captured.)