[reader9274]

There's a bug somewhere it seems like, as it ends the following game with "Illegal move, you lose", even though it's not an illegal move:

1. e2e4, e7e5 2. d2d4, e5d4 3. d1d4, a7a5 4. g1f3, b7b5 5. b1c3, a5a4 6. c3b5, a4a3 7. b5a3, a8a3 8. b2a3 --> Illegal Move You Lose. Game over.

FEN of game above: 1nbqkbnr/2pp1ppp/8/8/3QP3/P4N2/P1P2PPP/R1B1KB1R b KQk - 0 8

[oah]

a2a3 on the first move or on the second move after e2e4 outputs that you have played an illegal move.

But this is a bug as these are legal moves.

[foxglacier]

Simply using a2a4 as the first move does that too.

[reader9274]

ah interesting, a2a3 does the same. May be a bug with moves on the a file by white