A key square near the enemy king attacked by two or more pieces from the active side, with no defenders — typically the mating square in an imminent forced mate.
SAE concept sae_21431 fires when a key square near the enemy king attacked by two or more pieces from the active side, with no defenders — typically the mating square in an imminent forced mate.. It appears in 18 of 9,950 Climbchess puzzles (0.2%), spanning ELO 734–2682 (median 992).
Free forever · no email · no signup · delete data anytime.
This page documents A key square near the enemy king attacked by two…, one of 4,505 interpretable chess concepts extracted from Leela Chess Zero via sparse autoencoders. The full feature description from our SAE labelling pipeline reads:
A key square near the enemy king attacked by two or more pieces from the active side, with no defenders — typically the mating square in an imminent forced mate.
This pattern fires in 18 of our 9,950 tagged puzzles. The puzzles where it appears span ELO 734 to 2682, with a median rating of 992. That distribution tells you whether this is a beginner cue or a master-level subtlety.
Pattern statistics
| Concept ID | sae_21431 |
|---|---|
| Puzzles where it fires | 18 |
| Min ELO | 734 |
| Median ELO | 992 |
| Max ELO | 2682 |
| Coverage | 0.18% of puzzle set |
Related concepts
The five concepts most often co-firing alongside this one (Jaccard similarity over the puzzle co-occurrence graph) are:
Example puzzles
Below are 10 puzzles spanning the rating distribution. Each links to its own page with full move list and related concepts.
- Puzzle zfPbz — ELO 734, themes: mate, mateIn1, middlegame, side to move: Black
- Puzzle zfPbz_F — ELO 734, themes: mate, mateIn1, middlegame, side to move: White
- Puzzle zuaIp — ELO 862, themes: backRankMate, endgame, mate, side to move: Black
- Puzzle zuaIp_M — ELO 862, themes: backRankMate, endgame, mate, side to move: Black
- Puzzle zx0VA_F — ELO 869, themes: backRankMate, endgame, mate, side to move: Black
- Puzzle ziE5Q — ELO 992, themes: anastasiaMate, endgame, mate, side to move: Black
- Puzzle ziE5Q_M — ELO 992, themes: anastasiaMate, endgame, mate, side to move: Black
- Puzzle zxQSz_F — ELO 1885, themes: endgame, mate, mateIn2, side to move: Black
- Puzzle zuc1B — ELO 2339, themes: endgame, equality, short, side to move: Black
- Puzzle zuc1B_M — ELO 2339, themes: endgame, equality, short, side to move: Black
How to use this page
If you want to train this pattern, open the Climbchess trainer and filter for puzzles tagged with this concept. The trainer surfaces them at the right difficulty for your current rating, and tracks how often you spot the cue versus miss it. You can also browse the related concepts above to see neighbouring ideas in feature space.
Climbchess concepts are not heuristics written by a human author. Each one corresponds to a single direction in the residual stream of Leela Chess Zero that activates on a specific board feature, then was labelled by reading the top-activating positions. This makes the catalogue exhaustive (every Leela-detectable pattern is in here somewhere) and falsifiable (you can replay our extraction).
Frequently asked
What is SAE concept sae_21431?
A key square near the enemy king attacked by two or more pieces from the active side, with no defenders — typically the mating square in an imminent forced mate. It is one of 4,505 interpretable features extracted from Leela Chess Zero's residual stream via sparse autoencoders, then labelled by reading the top-activating positions.
Where does this pattern appear?
In 18 tagged puzzles (0.2% of the set), spanning Lichess ELO 734 to 2682 with a median of 992.
How do I train it?
Open the Climbchess trainer and filter for puzzles tagged with this concept. The trainer adapts difficulty using your live recognition profile and tracks how often you spot the cue versus miss it.
Is it free?
Yes. Climbchess is free forever, with no account, email, or signup required. You can delete your data at any time.