ALS-XY-Wing
Extreme
Used by Smart Hint
Three Almost Locked Sets in a row: two outer sets hang off a middle "bridge" set, and a digit shared by the outer two must land in one of them.
- First colour in the chain
- Second colour in the chain
- Cells that establish the pattern
- Where the conclusion lands
- Candidate ruled out
How it works
- Three Almost Locked Sets — each one candidate short of being locked: A1 on {2, 6}, the bridge E1 on {6, 8}, and G1 + G2 on {2, 8, 9}.
- A1 and the bridge share 6, and every 6 in one sees every 6 in the other, so only one of them can use it — a restricted common. The bridge and G1 + G2 share 8 the same way.
- Now suppose 2 were false in BOTH A1 and G1 + G2. Losing a candidate locks an Almost Locked Set, so A1 would have to be 6 and G1 + G2 would have to use 8. That robs the bridge of both 6 and 8, leaving it one digit short — impossible.
- So 2 lands in A1 or in G1 + G2. H1 sees every one of those cells, so it can't be 2.