Answers.Body: <p>Black is down a piece in the diagram, so I guess that White's last move was a capture.  Maybe Black has just played Nf6-g4 or Ne5-g4, discovering an attack on the long diagonal while also threatening Nxe3 (though then Nxe4 or Nd3+/Nf3+ looks better), or maybe Black just played Bf8-g7 with his Bishop already on g4.</p>
  <p>This means that White has just played Bxg4, sacrificing the exchange, and the engine's &quot;!!&quot; annotation regards this as a strong move.  Since White cannot trap the remaining Black Bishop on a1, I figure that (as <strong>Ross Millikan</strong> suggests in a comment) the engine analysis continues Bc8, threatening to win the Ra8 and remain a piece up.  It costs Black at least two pawns to save the Rook -- not one with ...a5 or ...a6 because the Be3 controls a7.  After Bc8, Nd7; Bxb7, Rb8 (or Rd8); Bxc6, White ends up with two pawns for the Exchange, which is a small material advantage, and better than White would have without playing Bxg4.  This justifies an annotation of &quot;!&quot; if not &quot;!!&quot;.  (If Black answers Bxc6 with Rc8 then White can trade on d7 and then save the c-pawn, probably with either c4 or Nc4.)</p>
  
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2024-04-19T18:24:03.013Z
Answers.LastActivityDate: 2024-04-19T18:24:03.013Z
Answers.UserDisplayName: Noam D. Elkies
Body: <p>Is this a blunder ?
  Bg7xa1.</p>
  <p>What next ?</p>
  <p><a href="https://i.sstatic.net/9f6Vc.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/9f6Vc.png" alt="enter image description here" /></a></p>
  
Comments.ContentLicense: CC BY-SA 4.0
Comments.CreationDate: 2024-04-19T03:09:45.843Z
Comments.Text: I accept my opponent's resignation for an illegal move.  Do you mean Bg7xa1?  The piece on h8 is the same color as the bishop.  Presumably White is planning Bc8 to win the a8 rook.
Comments.UserDisplayName: Ross Millikan
Comments.ContentLicense: CC BY-SA 4.0
Comments.CreationDate: 2024-04-19T05:09:32.553Z
Comments.Text: @RossMillikan only the second illegal move loses, at least in FIDE standard :)
Comments.UserDisplayName: Matija Sirk
Comments.ContentLicense: CC BY-SA 4.0
Comments.CreationDate: 2024-04-19T15:04:26.787Z
Comments.Text: This question needs work: As noted in another comment, g7xh8 is not a legal move as you aren't allowed to capture your own pieces. Also, are you asking if white's Bg4 was a brilliant move, asserting that  Bxa1 (assuming that's what you meant) is a refutation? Or are you asking if black playing Bxa1 (presumably) is a brilliant move?
Comments.UserDisplayName: GreenMatt
Tags: <analysis><blunder>
Title: A blunder or a brilliant move?
ThreadText: # A blunder or a brilliant move?
  
  (Asked by: username_0 on 2024-04-18)
  
  Is this a blunder ?
  Bg7xa1.
  
  What next ?
  
  [![enter image description here](https://i.sstatic.net/9f6Vc.png)](https://i.sstatic.net/9f6Vc.png)
  
  **Tags:** analysis, blunder
  
  > **Comments:**
  > **username_1**: I accept my opponent's resignation for an illegal move.  Do you mean Bg7xa1?  The piece on h8 is the same color as the bishop.  Presumably White is planning Bc8 to win the a8 rook.  
  > **username_2**: @username_1 only the second illegal move loses, at least in FIDE standard :)  
  > **username_3**: This question needs work: As noted in another comment, g7xh8 is not a legal move as you aren't allowed to capture your own pieces. Also, are you asking if white's Bg4 was a brilliant move, asserting that  Bxa1 (assuming that's what you meant) is a refutation? Or are you asking if black playing Bxa1 (presumably) is a brilliant move?  
  
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  ## 1 answers
  
  ### Answer by username_4 on 2024-04-19. Score: 2
  
  Black is down a piece in the diagram, so I guess that White's last move was a capture. Maybe Black has just played Nf6-g4 or Ne5-g4, discovering an attack on the long diagonal while also threatening Nxe3 (though then Nxe4 or Nd3+/Nf3+ looks better), or maybe Black just played Bf8-g7 with his Bishop already on g4.
  
  This means that White has just played Bxg4, sacrificing the exchange, and the engine's "!!" annotation regards this as a strong move. Since White cannot trap the remaining Black Bishop on a1, I figure that (as **username_1 username_1** suggests in a comment) the engine analysis continues Bc8, threatening to win the Ra8 and remain a piece up. It costs Black at least two pawns to save the Rook -- not one with ...a5 or ...a6 because the Be3 controls a7. After Bc8, Nd7; Bxb7, Rb8 (or Rd8); Bxc6, White ends up with two pawns for the Exchange, which is a small material advantage, and better than White would have without playing Bxg4. This justifies an annotation of "!" if not "!!". (If Black answers Bxc6 with Rc8 then White can trade on d7 and then save the c-pawn, probably with either c4 or Nc4.)
  
  
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