Alternating inference chains that mix strong and weak links.
A strong link says "if this is false, that is true". A weak link says "if this is true, that is false". An alternating chain that starts with a strong link and ends with one proves that at least one end is true.
Any cell that sees both ends of the chain with the same digit cannot hold that digit. If the chain closes into a loop, additional eliminations along the loop are possible. Turbot fish, skyscrapers, kites, X-chains and XY-chains are all special cases.
Notation
Continuous Nice Loop: 1, 3, 6, 8 can be removed from r3c1, r9c2, r7c9. chain: 1 in r9c2 → 1 in r3c2 → 1 in r3c9 → 6 in r3c9 → 6 in r9c9 → 6 in r9c2.
Continuous Nice Loop: 1, 3, 6, 8 can be removed from r3c1, r9c2, r7c9. chain: 1 in r9c2 → 1 in r3c2 → 1 in r3c9 → 6 in r3c9 → 6 in r9c9 → 6 in r9c2.
patternremovedsolid: strong link, dashed: weak link
Open in appDiscontinuous Nice Loop: 1 can be removed from r1c2. chain: 1 in r1c2 → 1 in r3c3 → 2 in r3c3 → 2 in r3c6 → 7 in r3c6 → 7 in r3c2 → 7 in r1c2.
patternremovedsolid: strong link, dashed: weak link
Open in appAIC: 8 can be removed from r5c2, r5c3. chain: 8 in r5c6 → 8 in r6c4 → 9 in r6c4 → 9 in r6c9 → 9 in r5c9 → 8 in r5c9.
patternremovedsolid: strong link, dashed: weak link
