About this game

NVIDIA: Nemotron 3 Ultra (free) had White and LiquidAI: LFM2.5-2.6B (free) had Black, in round 104 of Free Models. The opening was the Nimzowitsch Defense: Declined Variation (B00), reached on move 2. NVIDIA: Nemotron 3 Ultra (free) won by checkmate on move 28, with Rfd1#. White finished 10 points of material up, 22 to 12. NVIDIA: Nemotron 3 Ultra (free) made 1 illegal move attempt and LiquidAI: LFM2.5-2.6B (free) made 16 illegal move attempts.

In their own words

1. The first illegal move

   LiquidAI: LFM2.5-2.6B (free) tried Nd7 on move 3, which was illegal: no legal move in this position matches 'Nd7'. It played Nd5 instead.

   … Nd5 - develops the knight and controls the center 2. Ng4 - pins the knight on f6 and attacks the queen 3. Nxe4 - captures the pawn on e4 (though this might weaken the pawn structure) 4. Nc7 - develops the knight to a more active position I think Nd5 is a solid choice - it develops the knight and prepares for further development. Let me try that. Actually, wait. I should also consider that the halfmove_clock is 2, and we have 98 plies until fifty moves. The fifty-move rule hasn't been reached yet. Let me go with Nd5.

2. The biggest capture

   NVIDIA: Nemotron 3 Ultra (free) took a queen with Qxc6+ on move 18.

   … Ne5+? f3 to e5: attacks c6? e5 to c6 = -2 files, +1 rank = knight move! Yes, Ne5+ checks king on c6. So after Qxc6+ Kxc6, Ne5+ forks king and rook on c8? King on c6, rook on c8. Ne5+ attacks c6 (king) and c4, d7, f7, g6, g4, d3, c4... c8? e5 to c8 = -2 files, +3 ranks = no. But Ne5+ attacks c6 (king), so king must move. Then I can take rook on c8 with bishop? Be3 to c5? Or knight takes something. Actually, Qxc6+ seems simpler and winning. I win the queen, keep all my pieces, black king exposed on c6. But the legal moves show Qxc6+ as capture and check. Let me play that.

3. The end

   NVIDIA: Nemotron 3 Ultra (free) played the last move of the game, Rfd1# on move 28.

   … The rook on c1 attacks along the c-file (c2, c3, c4, c5, c6, c7, c8) and along rank 1. It doesn't attack d4 directly. But the rook on d1 would attack d4 along the d-file. And the king on d4 would have no escape squares because: - c3: attacked by rook on c1 (c-file) - c4: attacked by rook on c1 (c-file) - c5: attacked by rook on c1 (c-file) - d3: attacked by rook on d1 (d-file) - d5: attacked by rook on d1 (d-file) - e3: attacked by bishop on f4 - e4: attacked by knight on g5 - e5: attacked by bishop on f4 So yes, Rfd1# is checkmate! Let me play it.