Welcome to Clue Boxes! I came up with this Sudoku series based on wooden puzzle boxes, where one small discovery leads to the next. Each puzzle works in a similar way: follow the clues, unlock the next step and see where they take you.
Rules:
Normal sudoku rules apply
Fog: All but one of the puzzle boxes are closed 'fog'. Fill in the correct numbers for the boxes to open.
Zipper lines: Digits an equal distance away from the center of a red zipper line sum to the value in the centre of the line (marked with a circle). For even length zipper lines this will be the sum of the two center cells
Killer cages: Digits in a cage sum to the small clue in the cage's top-left corner. Digits may not repeat within a cage.
Global Modulo-3: Each 2x2 box in a grid must contain a digit from each modulo 3 set: {1,4,7}, {2,5,8} and {3,6,9}.
Enjoyed this one? See the other puzzles in the Clue Box series:
Clue Box #1: a Renban German Whisper puzzle.
Clue Box #2: a Regional Sum Dutch Whisper puzzle.
Solution code: Row 9, left to right
today, 13:36 by Twan2797
Clarified rules
yesterday, 15:01 by Merovius
The rules for zipper lines do not cover what happens at zipper lines of even length (as there is no value in the center).
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Agreed, I have clarified the rules.
on 22. July 2026, 03:13 by kisukeA
Fun series, I'd rate this one a bit easier than the last one, 2* for me