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.
Candidate-map demonstration
The violet cells mark the pattern and the gold cell marks the resulting placement or elimination. Treat this compact map as orientation; use the verified full puzzle below to practise the actual deduction.
••••
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.
VERIFIED PRACTICE
XY-Chain training
Loading a mathematically verified puzzle state…