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Having been beaten at your favourite pencil and paper game, Noughts and Crosses, repeatedly by your friend, you decide to give up on your dreams of becoming Tic-Tac-Toe world champion.

However you come home to a note from your friend... (click for larger version)

enter image description here

Rolling your eyes at the 'xo' pun, you take a look at the note (google sheets link). A bunch of grids? Most of these don't even make sense!

But then again, you really want that world championship, so you should probably take all the advice you can get...


Solve the puzzle to get a bit of Tic-Tac-Toe advice!

Hint:

Odd how only the first two columns of each grid has Xs in them... can you see why?

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  • $\begingroup$ Might the 12th grid in the top row be missing something? $\endgroup$
    – caPNCApn
    Sep 9, 2022 at 22:20
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    $\begingroup$ @cap whoops - good spot, missing an O - will fix $\endgroup$ Sep 9, 2022 at 22:27
  • $\begingroup$ Might the 4th grid in the bottom row be missing something that the 5th grid has but shouldn't? $\endgroup$
    – caPNCApn
    Sep 9, 2022 at 23:16
  • $\begingroup$ @cap nope, double checked bottom row and all good. I'm assuming you've made some decent progress, and if you're at the end then try colouring in X and O to see if it makes it clearer - you'll know when you have the answer! $\endgroup$ Sep 9, 2022 at 23:25

1 Answer 1

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First, as clued in the hint,

we decode the Xs in the upper row as Braile (as @Nautilus has done) and we get the string USE NEXT TURN X IS ONE O IS ZERO (spaces added)

Looking at the grids in the first row, we note that

There are either the same number of Xs and Os, or one more X than O. From this we assume that X always starts. So an even number means X is next and an odd number means O is next.

enter image description here

Interpreting

the next X or O from each grid as a binary digit in 3 8-bit bytes, we get 01011000 01001111 01010010 and taking the ASCII characters for them yields the 3-character string XOR.

Looking at the bottom row of grids

we realize they are only Xs. We XOR them with the first row of grids to get the following

enter image description here

which seems to say ALWAYS GO IN THE CORNERS! Apt Tic-tac-toe advice!

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  • $\begingroup$ Good job! Well explained, thats the answer I was looking for - mind if I add a couple small diagrams too? Oh, and realised the issue with the XOR, try with the next move included, think thats where the difference is :) $\endgroup$ Sep 9, 2022 at 23:47
  • $\begingroup$ @BeastlyGerbil Ah! That makes sense. Please, feel free. I can update mine too if you like. $\endgroup$
    – caPNCApn
    Sep 9, 2022 at 23:50
  • $\begingroup$ Made a couple minor changes, realised the final answer can be very hard to see with Xs and Os, so added a colourised version - all correct now, great job! $\endgroup$ Sep 9, 2022 at 23:52
  • $\begingroup$ @BeastlyGerbil Thank you, looks good. I realize now I skipped part of the solution process. It looks like rot13(rnpu arkg zbir (abg bayl tbrf va gur pbeare ohg nyfb) rvgure jvaf be ceriragf ybff. Rkprcg va gur 19gu tevq. V'z abg n GGG rkcreg. Vf gurer n cnegvphyne ernfba sbe gung zbir?) $\endgroup$
    – caPNCApn
    Sep 10, 2022 at 0:06
  • $\begingroup$ That part is not particularly important to the solution, in fact isn’t needed at all if you just count the Xs and Os instead, but I wanted to have the next move in the same space just for sort of aesthetics, and usually the best way to do that was to win or prevent a loss. Unfortunately the Braille ‘V’ scuppered that a little bit, so I didn’t put too much importance on it, just a little Easter egg really :) $\endgroup$ Sep 10, 2022 at 0:12

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