Expert Techniques

Expert Hint runs bounded fallback searches only when the normal logical strategy list cannot find a step. These hints are intentionally budgeted so the web UI stays responsive.

When to look for it

Use Expert Hint when the puzzle still has candidates but ordinary hints return no progress. Expert techniques are proof-oriented: they explain what every valid branch has in common, rather than naming a small local pattern.

Implemented in Xodoku

• Templates enumerate valid placements for one digit and remove candidates that appear in no valid placement.
• Forcing Chain follows two-way assumptions from a candidate or cell and keeps conclusions shared by every branch.
• Forcing Net allows branching through cells with more than two candidates, then intersects the resulting conclusions.

Reserved

• Kraken Fish is reserved for a later Fish-rooted forcing proof. Xodoku can already find complex fish and forcing deductions, but it does not currently combine them into a named Kraken Fish hint.

Search budget

The web solver stops expert search after a small deadline and node budget. A truncated search is reported separately from a complete search that found no hint.