Logic Masters Deutschland e.V.

Photocopied Series #2: Coffee Troubles

(Published on 14. May 2026, 00:46 by gkammer)

This is part 2 in a series of related puzzles. You can see all the puzzles in this series on my website at kammer.xyz/blog/sudoku/photocopied.

You can also visit the logic-masters pages for the other puzzles in the series:

You have been gifted a large collection of puzzles from a friend. You sift through them looking for interesting ones and find photocopies of puzzles from an old book of puzzles, filed under "puzzles with no given digits". The original book is nowhere to be found and the photocopies are in black and white.

In this specific puzzle, to make matters worse, in box 3, a coffee stain has covered 3 cells. You suspect there may have been clues under the stain, but you can't make them out. At least you can make out that there are no lines connecting any of those cells to any of the adjacent uncovered cells (e.g. there is no line connecting R1C8 to R1C7).

You can see the original photocopies on the webpage linked above, but the images are too large to upload here

You assume the original had a unique solution, but can you still reconstruct that solution? The rules below are listed for the entire section of puzzles, so you can't be sure whether all three line types actually exist in any of the puzzles.

  • Normal sudoku rules still apply.
  • Renban: Digits along a purple line form a set of consecutive digits in any order.
  • German whispers: Adjacent digits along a green line have a difference of at least 5 (2 for 4x4 puzzles).
  • Equal-sum lines: Box borders divide a blue line into multiple segments which have the same sum. Different lines may have different sums.

Your goal is to figure out what the original solution to each puzzle was. I have transcribed this puzzle and put it on sudokupad for your ease of solving!

Solution code: 7th row, left to right

Last changed on on 4. August 2026, 22:15

Solved by TheCutmaster, jmw, Briks, SKORP17, Hagemann, Montikulum, MrQubo
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Comments

Last changed yesterday, 10:11

yesterday, 10:08 by MrQubo
Very clever and interesting ruleset. Requires quite a lot of thinking to even start the puzzle, but once I got it the solve went smooth and quickly.

Though, I realized I did not got the rules exactly right at the end of the solve. But I believe the rules are precise, it's just that I understood it wrongly.

on 4. August 2026, 22:15 by gkammer
Fixed a couple minor things in the description.

on 25. July 2026, 19:42 by gkammer
Made an implicit assumption more explicit.

on 22. July 2026, 20:07 by gkammer
Edit: Changed photos slightly

on 22. July 2026, 20:01 by gkammer
Edit: this puzzle is now part of a series of puzzles. I have added references to the rest of the series.

Last changed on 14. May 2026, 14:12

on 14. May 2026, 14:09 by gkammer
Blueberrypug, it can't be a renban line, but it could just happen to also contain digits in sequence that could satisfy renban. You should pretend there was an original puzzle called "Line Dancing" with the given lines, and that if a line is a region sum, it doesn't say anything about those digits not being a renban. And jmw, your edit is correct.

Last changed on 14. May 2026, 05:27

on 14. May 2026, 05:19 by blueberrypug
oh okay so if a line is a region sum for example, it cant also be say a valid renban at the same time?

on 14. May 2026, 04:18 by gkammer
No, each distinct line you see is one color.

on 14. May 2026, 03:10 by blueberrypug
can lines be multiple different types of lines?

Difficulty:4
Rating:N/A
Solved:7 times
Observed:0 times
ID:000STB

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