Mistakes and How to Debug Failed Attempts
Recover quickly without nuking your progress.
1) Spot the contradiction
Look for illegal adjacencies, unreachable next-number routes, or isolated pockets created by your last moves.
2) Rewind to last fork
Undo to the most recent choice that created multiple options. Try the alternative and re-check reachability.
3) Re-validate invariants
- Every cell remains coverable.
- Numbers stay connectable with a simple path.
- No branch would force revisiting a cell.