A few moderators from Stack Exchange communities decided to go "old-school" and developed a desktop application for Stack Exchange. You, as an enthusiastic user, of course want to try it out. Everything worked fine for the most part, but suddenly an error dialog pops up:

An unsuspicious image description

Note: The typo in "occurred" is unintentional, maybe I will fix it later, but it isn't important to the puzzle anyway.

Apparently the developers have a sick kind of humor... But you decide to play along. You must figure out what the exception is, and judging by the last sentence of the message, you're not allowed to view the source code (which should be obvious anyway...).

The grid also seems to be important. It's made of 7 rows and 7 columns, and a gray object is moving across the grid, stopping & blinking at specific coordinates.

List of points where the object stops (in order):



The developers like to proudly show everyone that they're the mods of SE communities.

What is the actual exception the error dialog is trying to display?

  • 4
    $\begingroup$ Nice GIF! Bit of a shame you posted the numbers by the way - would have been fun to figure out $\endgroup$ – Beastly Gerbil Sep 5 '16 at 20:17
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    $\begingroup$ I think it's actually better that you left them in. Makes it more accessible. $\endgroup$ – Deusovi Sep 5 '16 at 20:21
  • 1
    $\begingroup$ I agree with @Deusovi to some extent. If the object had been moving slower then you could have left out the list, but its moving pretty fast so I think it would be tricky to get them and people would make mistakes at that speed $\endgroup$ – Beastly Gerbil Sep 5 '16 at 20:22
  • 6
    $\begingroup$ @Deusovi I agree. In Firefox I have image.animation_mode set to "none", so the explicitly stated list of coordinates gives vital info that is not otherwise accessible. Lukas or anyone -- if you make a puzzle, please do not put information in animation which is not also in the text or static images. $\endgroup$ – Rosie F Sep 5 '16 at 20:49
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    $\begingroup$ How I found out about Playfair was mainly by noticing the paired-up nature of the enciphered message - and also the "stay fair" in the image. Maybe that means the key is "my friend"? $\endgroup$ – Rand al'Thor Sep 6 '16 at 0:14

The clues in the question

  • From the paired-up nature of the enciphered message, and also the words "stay fair" in the text of the error popup message, I concluded that

    this is something to do with the Playfair cipher.

  • This cipher needs a key, and my best guess at the key is, in true West-Gate-of-Moria fashion,

    MYFRIEND, because then the phrase "I want you to stay fair, my friend" in the text of the error popup is a double clue rather than just one.

  • The hint now added to the question gave me the idea of

    using a diamond shape somehow, since SE moderators all have diamonds next to their usernames.

  • The OP also mentioned, after I'd posted the first version of this answer (attempting to use the above-mentioned cipher directly on the cells of the 7x7 square provided in the question), that

    the Playfair part of the solution is to be done using a standard 5x5 square, and the ciphertext first needs to be found using the 7x7 grid provided.

The solution method


write out the alphabet (missing J, as is standard in Playfair ciphers) in a diamond within the 7x7 grid provided:

* * * A * * *
* * B C D * *
* E F G H I *
* R S T U V *
* * W X Y * *
* * * Z * * *

Then the given sequence of cells:

32 46 14 55 45 24 47 45 43 54 25 44 55 41 44 45 74 23 46 32


E P A U O C Q O M T D N U K N O Z B P E.

Plug this into

a standard 5x5 Playfair square with the key "my friend" (this can be done quickly using the online tool here, or you can do it by hand to check)

to get the final solution:


  • $\begingroup$ The playfair part is actually to be solved with a standard 5x5 keyed alphabet square, so you have to find the string to decrypt using the 7x7 grid. $\endgroup$ – user14478 Sep 6 '16 at 7:12
  • $\begingroup$ Very good. The diamond shape might have been more obvious if the cursor never moved outside it. But that's just a quibble and only something I noticed after the puzzle was solved. $\endgroup$ – M Oehm Sep 6 '16 at 17:36

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