I was playing against the online version of Shredder on the hard setting, and after this weird opening phase I went ahead with a queen trade, but weirdly Shredder didn't take my queen. Is this just a glitch, or is there some feasible strategy behind this move? The pawns aren't really a threat to my king; I'm not locked in and there is no support for the attack.

[Event "?"]
[Site "?"]
[Date "?"]
[Round "?"]
[White "Shredder"]
[Black "Me"]
[Result "?"]
[fen ""]
[Startply "1"]

1. d4 d5 2. c4 dxc4 3. e4 Nf6 4. e5 Ne4 5. f3 Qd5 6. fxe4 Qd5xe4 7. Ne2 Bg4 8. Nc3 Qc6 9. d5 Qc5 10. Qd4 Qc5xd4 11. e6?
  • 2
    Looks like White playing badly (a sign that the engine is handicapped and not playing at full strength?), although I am not sure what you're asking because you didn't offer a queen trade, and White has no chance to take your queen.
    – Allure
    Apr 19 at 3:56
  • 1
    @Allure I had some errors in the move notation; I got it working correctly now. Apr 19 at 4:01

1 Answer 1


Chess computers have the ability to beat any human player with extreme ease, so in order to give you a chance and make the game interesting, they need to play bad moves on purpose.

The problem is that computers aren't good at making mistakes in a way that would imitate those made by humans, so they'll just introduce random blunders in their otherwise perfect-ish play.

This is one of those cases. There is absolutely no logic behind this last move from White. Now you can simply take the knight with your bishop to remove the threat on your queen and have a totally winning position

  • I don't know how this particular engine works, but as a programmer, I got to say I disagree with your logic about difficulty. Chess engines are made "dumber" by limiting the time they have to search the solution space. Imagine a giant tree that starts from the current position, and then looks at all the moves you can make, and moves you can make from that move etc. You will limit the engine's cleverness by limiting how many moves deep it can build this three. But that should never produce dumb and illogical moves that have no possible payoff.
    – Davor
    Apr 19 at 12:46
  • 1
    @Davor try playing a game against one of the lower bots on chess.com or level 1 Stockfish on lichess and you'll see that they're different from just a traditional engine with capped time/depth
    – David
    Apr 19 at 13:04
  • @Davor A common way that engines adjust their strength is to get the scores for all of the possible moves in the root position and then add a random number to the scores for all but the best move. It then chooses to play the move with the highest score after this adjustment. The difficulty levels differ based on how large of a random number can be generated to add to the score.
    – Nelson O
    May 11 at 14:29

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