Proven Sudoku
Techniques / Exotic and rank-zero
Broken Wing
Also called Guardian, Turbot Guardian, Broken Wing pattern.
New to this shorthand? How to read a sudoku grid explains r4c7, houses, candidates and the rest.
What it means
A ring of squares where one number would have nowhere to go if the ring were perfect. One square breaks the ring, and that square is forced to take the number.
The exact rule, for stronger players
The rule, stated exactly: An odd-length loop of conjugate links on one digit cannot be satisfied, so at least one guardian, a candidate breaking the loop, must be true. Cells seeing every guardian lose the digit.
What it removes: Remove d from cells seeing every guardian.
Why it works: An odd cycle cannot two-color. The guardians are the candidates whose presence breaks the cycle, and at least one must hold.
Worked examples
None yet. This pattern does not turn up in our daily boards, so there is no real example to show. We would rather wait than draw a fake one.
Learn these first
- Simple ColoringPick a digit.
- X-ChainA chain about one number only.
Related exotic and rank-zero
- Domino LoopA ring of pairs that lean on each other all the way round, like falling dominoes.
- Double ExocetTwo of those launcher patterns sharing the same numbers.
- FireworksA number is trapped so that it can only sit in one row, one column, or the square where they cross.
- Gurth's Symmetrical PlacementSome puzzles are built with a mirror pattern.
- Homogeneous ChainsA chain where every link is the same kind.
How often does it come up?
Our rough estimate: uncommon. Guardian logic generalizes several other patterns.