Variant Sudoku 101: Renban Lines
(Published on 11. December 2025, 22:24 by PhoenixAki)
My Variant Sudoku 101 series introduces common variant sudoku rules, frequently using dynamic fog to help point the solver where to look next. The target audience is those who are comfortable with classic sudoku, but new to variant sudoku. In other words, you are expected to be able to identify things like (but not limited to) pairs and triples in rows/columns/boxes and know how to take advantage of them. I welcome everyone to try this series regardless, just be warned you may have a harder time if you're new to sudoku in general.
- Normal sudoku rules apply. Place the digits 1-9 in each row, column, and 3x3 box without repetition.
- Dynamic Fog: The grid is partially covered in grey fog. Placing correct digits will clear the fog, at minimum under that cell and sometimes in other parts of the grid. No guessing is required.
- Renban: Digits placed on purple lines must be a non-repeating set of consecutive digits in any order. For example, a 3-cell line could contain the digits 456, arranged as 456, 564, 465, etc.
To increase accessibility to my puzzles, I include hints in my puzzle posts (see below). I also post solution videos on my Patreon and YouTube channel. Puzzles released prior to February 2026, as well as my snackdoku and variant sudoku 101 series will continue to get public solution videos on YouTube, while others will be Patreon-exclusive.
Hint 1: There are 2 given 9's in the grid. What impact do they make on the renban lines in rows 1 and 9?
Hint 2: Once you have the pairs of digits for each corner of the grid, think about how the verticle renbans in columns 1 and 9 interact with that information.
Hint 3: There's 2 triples of digits looking at box 5 now. What does that mean about R5C5?
Hint 4: Past this point, most of the renbans can be resolved simply by carefully pencilmarking them. General tip is to try to prove when the extreme cases aren't possible. For example, a 3-cell renban that has a 5 on it could potentially go up and be 567. But if you can prove that 7 can't go on it, that in turn proves there must be a 4 on it (in which case it'd be 456). Frequently, ruling out a number from a short renban has the inverse effect of proving a different digit must be on it.
Solution code: Box 2's digits in normal reading order (left to right, top to bottom). 9 digits.
Comments
on 28. January 2026, 01:25 by PhoenixAki
Added links to Patreon.
on 22. January 2026, 02:58 by PhoenixAki
Added hints after learning recently how to do that in HTML. Wish I knew this a few weeks ago when I went over all my posts...oh well.
on 5. January 2026, 22:45 by PhoenixAki
Updated post as part of an effort to improve consistency of rule phrasing and post layout across all my puzzles.
on 17. December 2025, 03:15 by byale
nice puzzle! 21:43
on 16. December 2025, 22:23 by philolologue
18:40 for me :) loads of fun, thank you!
on 14. December 2025, 06:39 by ZiiNerD
20:48 for me! I think renbans tend to not have obvious deductions for my brain, but I was able to get the break-in paying attention to the possibilities. Well set and a nice intermediate level puzzle that is approachable for newcomers like me! Thanks for the puzzle, PhoenixAki!
on 13. December 2025, 00:02 by PhoenixAki
I've realized now there's a much easier way of phrasing/seeing the break-in compared to what I was envisioning when I set it, and that's probably why the hint hasn't been necessary for people so far seemingly. Ah well. Crazy how you can take the same deduction and phrase it in different levels of difficulty depending on how you look at it.
on 12. December 2025, 15:32 by Myfyr MJ
Very nice and easy, thank you. Took me 12 minutes.
