Proven Sudoku
Letter-named wings (M, S, L, H, Split, Hybrid, Local)
Also called M-Wing, M Wing, S-Wing, S Wing, L-Wing, L Wing, H-Wing, H Wing, Split Wing, Split-Wing, Hybrid Wing, Hybrid-Wing, Local Wing, Local-Wing.
New to this shorthand? How to read a sudoku grid explains r4c7, houses, candidates and the rest.
What it means
Short chains that people gave letters to. Two squares with two numbers each, joined by a link, and following the links forces one end to be a certain number, so any square seeing both ends loses it. The letters describe the shape, not the reasoning, and the reasoning is the same every time. Learn it once and you will spot all of them, whatever a book calls the one in front of you.
The exact rule, for stronger players
The rule, stated exactly: A family of named length-four alternating inference chains, each combining a bivalue cell with a conjugate pair or a second bivalue cell so that the two endpoints share a digit, licensing elimination of that digit from cells seeing both endpoints. The members differ only in which node types sit where, and several are the same pattern under different names.
What it removes: Remove the shared endpoint digit from cells seeing both endpoints.
Why it works: One argument covers every member: standard AIC endpoint reasoning over a chain of length four with mixed node types. Whichever end is false forces the other true, so any cell seeing both endpoints cannot hold the shared digit.
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
- W-WingTwo squares far apart hold the same two numbers.
Related wings
- Remote PairsA string of squares that all hold the same two numbers, each one linked to the next.
- VWXYZ-WingThe same idea stretched to five squares and five numbers.
- WXYZ-WingFour squares holding four numbers between them.
- XY-WingThree squares, each with two numbers left.
- XYZ-WingLike the XY-Wing, but the middle square has three numbers instead of two.
How often does it come up?
Our rough estimate: uncommon as named patterns. Most solvers meet these as ordinary AICs and never reach for the letter.