LEVEL 8
XY-Chain
A chain of bivalue cells links matching endpoint candidates.
How to find it
- Start with a bivalue cell and follow shared candidates.
- Alternate through bivalue peers without breaking the chain.
- Eliminate the endpoint candidate from common peers.
Logical demonstration
The violet cells represent the pattern; the gold cell represents the resulting placement or elimination. Verify every highlighted candidate belongs to the required houses before acting.
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Common mistakes
- Using cells that do not share the required row, column, box or peer relationship.
- Removing a candidate before confirming every occurrence in the pattern.
- Confusing a possible pattern with a completed logical proof.
GUIDED PRACTICE · EXERCISE 1 OF 3
XY-Chain training
Identify the logically justified next action. Violet cells form the pattern and the gold cell is the proposed result.
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