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What secret code is hidden in this masyu puzzle?

Note: The regions marked with x are not to be drawn

  • 8
    $\begingroup$ Please forgive me if I'm wrong, but I'm not convinced this 'masyu' puzzle has a unique logically deducible solution... I'm failing to see much beyond this. My suspicion is that this is instead intended to conceal rot13(n zrffntr va Oenvyyr) but I'm not seeing a way to apply it consistently across the whole puzzle. $\endgroup$
    – Stiv
    Commented Oct 21, 2020 at 9:49
  • $\begingroup$ You can try to link the others together, it will reveal a (Sbhe ahzore) code $\endgroup$
    – 00xxqhxx00
    Commented Oct 21, 2020 at 11:09
  • $\begingroup$ I found a legal solution where the hidden code is rot(guerr, svir, qbt, pnpghf) $\endgroup$
    – IanF1
    Commented Oct 21, 2020 at 15:17
  • 1
    $\begingroup$ If I'm not mistaken, even the updated one is still not uniqely solvable.. (I can't go further than this one: imgur.com/a/O4fazI9). $\endgroup$
    – athin
    Commented Oct 22, 2020 at 2:08
  • 4
    $\begingroup$ @00xxqhxx00 As a puzzle creator (especially for grid deduction puzzles), you're not supposed to "hope this works". It's your responsibility to check that it is uniquely solvable. $\endgroup$
    – Bubbler
    Commented Oct 22, 2020 at 3:56

1 Answer 1


The X's scattered all over the board makes it a rather dull and mechanical puzzle, and still there is an ambiguity at the lower left corner:

How to get to this point:

Observe that the X's make the entire cell unusable, and therefore they act like the outer boundary for white/black pearls nearby. Specifically, if a white pearl is adjacent to an X, it means the line should pass straight through it in a specific way (e.g. horizontally if X is right above or below it). If a black pearl is adjacent to/one cell away from X, the line should extend from it two units in the opposite direction. Once this step is complete, proceed with usual single-loop deductions: avoid making a closed loop too early or making a dead end.

Assuming the edge goes straight vertically so it looks like this:

then the secret code is

3564, reading the digits horizontally. Note that the digit shapes overlap a little bit.


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