Kropki Nabner Loop
(Published on 27. September 2025, 02:48 by yttrio)
Rules:
Normal Sudoku rules apply: place the digits 1-9 in every row, column, and 3x3 region.
Draw a one-cell-wide loop of orthogonally connected cells. The loop may not touch itself, not even diagonally.
3x3 region borders divide the loop into segments. Every loop segment acts as a Nabner line: no two digits on a segment can be consecutive, regardless of their position on the segment. A 3x3 region can have multiple segments, and single-cell segments inherently satisfy this constraint.
Digits separated by a white dot are consecutive. Digits separated by a black dot have a ratio of 2:1. Not all possible dots are necessarily given.
For each given dot, at least one of the digits touching the dot must be on the loop.
Solution code: Digits on the loop in row 8 (left to right) followed by digits on the loop in column 5 (top to bottom)
Comments
yesterday, 17:16 by BrianO
Found this puzzle by accident, and it's wonderful. Like others have said - Nabner lines can be a bit of a slog sometimes, but this makes them feel elegant and cool.
yesterday, 08:41 by fitzie
This is absolutely a top puzzle for the year for me. Not that difficult, but really pleasurable solve, and very unique with common constraints.
on 28. September 2025, 23:48 by Draxie
Making Nabner's cool. No mean feat. Thank you.
on 28. September 2025, 23:38 by Draxie
Making Nabner's cool. No mean feat. Thank you.
on 28. September 2025, 09:29 by rhodri
This is so elegant. A complete joy
on 27. September 2025, 19:34 by Exigus
Very impressive setting. Thanks!
on 27. September 2025, 13:14 by Calvinball
Wowser Bowser! A nabner loop seems like a nightmare to be able to close cleanly, leave it to yttrio to pull it off.
on 27. September 2025, 05:04 by thrutch
A cracker, that. Nothing particularly hard, but several nice surprises.
