🧠 Sharing Space (Illegal Move Exercise)

Illegal Move Exercise: The audio will lead you through a series of moves from the beginning of a game. Somewhere in there, a player will make an illegal move but the game will continue anyway. Find the illegal move.

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PGN for today's exercise:

1. Nf3 Nf6 2. g3 d5 3. Bg2 Bd7 4. O-O Nbd7 5. d4 c5 6. dxc5 e6 *

And the answer is...
Black's move 4... Nbd7 is illegal because that square is already occupied by the light-squared Bishop.