Proven Sudoku
Continuous Nice Loop
Also called Continuous Loop, Nice Loop (continuous), AIC Loop.
New to this shorthand? How to read a sudoku grid explains r4c7, houses, candidates and the rest.
What it means
A loop where the reasoning closes back on itself with no weak spot. Because it never breaks, every link in the loop gives you something. It usually clears out more than a plain chain does.
The exact rule, for stronger players
The rule, stated exactly: An alternating inference chain that closes on itself with the alternation intact all the way round. Every weak link in the loop becomes an exclusive-or, licensing elimination of the linking candidate everywhere else in the house that link uses.
What it removes: For every weak link in the loop, remove the linking digit from all other cells of the house containing that link.
Why it works: A closed alternating loop forces exactly one of each strong-linked pair true. Each weak link therefore has exactly one true end, so the linking digit is fully consumed by the loop within that house.
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
- Alternating Inference ChainA chain that switches between two kinds of step.
Related chains
- Digit Forcing ChainTake one number in one square.
- Discontinuous Nice LoopA loop that almost closes but has one weak spot.
- Dynamic Forcing Chain with ContradictionAssume a digit is right.
- Dynamic Forcing Chain with Double ImplicationTry both options for a square and follow each one out fully.
- Forcing Chain (general form)Pick something and assume it.
How often does it come up?
Our rough estimate: uncommon, but a continuous loop usually produces several eliminations at once, which makes it high value when found.