Caissa Codex
D31

Queen's Gambit Declined: Semi-Slav, Koomen Variation trainer

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Type a move and press Enter: e4, Nf3, O-O, or from and to squares like g1f3 (e7e8q to promote). The board is also played with the mouse.

Practise the Queen's Gambit Declined: Semi-Slav, Koomen Variation

Play Black's moves of the line from memory — 1. d4 d5 2. c4 e6 3. Nc3 c6 4. Nf3 dxc4 5. e3 b5 6. a4 Bb4 7. Bd2 Qe7 — and the trainer plays White's replies; "Play the other side" turns it around.

Read about the line, its statistics on Lichess and Stockfish's evaluation on the Queen's Gambit Declined: Semi-Slav, Koomen Variation page, or pick another opening in the opening trainer.

https://chesscodex.org/train/queens-gambit-declined-semi-slav-koomen-variation