Search technique · Expert
Ariadne's Thread
Systematic, disciplined branching: pick an arbitrary but recorded starting point, follow it to either a solution or a contradiction, and unwind cleanly if it fails.
Why it works
Unlike ordinary guessing, this method is complete by construction. If a valid solution exists, following every branch in order, recorded and undone properly, is guaranteed to find it.
Trigger
The true last resort, on a puzzle that resists every other technique, and only after confirming it's genuinely required, not just difficult.
Common mistake
Confusing this with ordinary trial and error. The difference is discipline: a recorded branch point and a clean, complete unwind if it fails, not an informed guess you can't cleanly undo.
Example
Pick one unresolved cell, mark it true, record the exact state at that moment, and follow every consequence. If it contradicts, unwind to that exact recorded state and mark the cell false instead, now forced, not guessed.
On Bambleweeny's board
Not implemented in the live solver. Every Bambleweeny puzzle is built to be solvable without it — genuinely useful only on puzzles from less careful publishers.