Puzzle zu4Fq — ELO 1143
This is a White-to-move puzzle rated 1143 ELO. The first move is b5a6, tagged with 10 interpretable concepts and Lichess themes: crushing, defensiveMove, endgame.
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Position
White to move. ELO 1143. Themes: crushing, defensiveMove, endgame, long, pawnEndgame, zugzwang.
FEN: 8/2k5/1p5p/1K2p1p1/1P2P1P1/7P/8/8 w - - 3 35
Show solution (6 ply)
Try to find the move yourself first — look for the rarest concept firing on this position before peeking. Solution sequence: b5a6 c7c6 b4b5 c6c5 a6b7 c5b5
Concepts that fire on this position
Our SAE pipeline tagged this position with 10 active features. Each links to a page documenting that pattern in detail.
Why this puzzle is hard
The rarest pattern firing here is A pawn on the 4th or 5th rank is attacked by an enemy pawn and defended by a…, which appears in only 27 of our 9,950 puzzles (0.27%). Rare patterns tend to be the bottleneck — players who haven't internalised them will fail this puzzle even when their tactical calculation is otherwise solid.
The puzzle's Lichess ELO of 1143 reflects this: solvers below that rating typically miss the cue entirely.
Similar puzzles
Puzzles sharing the most concept tags with this one — a stronger signal than theme overlap because it reflects the actual patterns Leela recognises.
Train this pattern
Click through to the Climbchess trainer to attempt the position interactively against the same Leela network that tagged it. The trainer adapts difficulty using your live concept-recognition profile — it surfaces puzzles tagged with concepts you've been missing, not random brawls.
If you want the underlying methodology, the how-it-works page walks through the SAE training run, the labelling pipeline, and the puzzle-tagging procedure end-to-end.
Frequently asked
What is the rating of this puzzle?
1143 Lichess ELO. Solvers below that rating typically miss the key cue.
Which side moves first?
White to move; the first move of the solution is b5a6.
What concepts does it train?
10 SAE-derived patterns including A king is placed on a low rank (1st or 2nd) in an endgame…; Detects a king on the back rank (rank 1 or 8) with no…; A pawn on the 4th or 5th rank is attacked by an enemy pawn….
Can I attempt it without an account?
Yes — Climbchess requires no signup or email. Click the trainer link to play the position interactively.