While walking through the PSE lounge, I noticed a piece of paper on one of the tables. Picking it up, I saw several things. The first, was a couple of sentences at the top:

I love this place! But it really needs to upgrade its...

After that followed what appeared to be a Sudoku.

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It seemed to be missing quite a few numbers for it to give a unique solution. It had some odd yellow squares, though.

Below the Sudoku was something which was clearly a Nonogram.

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Below the nonogram was some text.

Crosses are red
Violets are blue
I suck at rhymes
But this is a clue

Below this were the letters CM. Perhaps the initials of the person who wrote this? Can you help me make sense of this?

What exactly did the author think should be upgraded?

  • 1
    $\begingroup$ Great puzzle! I love how everything fits together. $\endgroup$ – Rand al'Thor Apr 13 '20 at 3:30
  • $\begingroup$ Thanks! This was my first "story" puzzle. Actually quite a lot of fun to make! $\endgroup$ – Jens Apr 13 '20 at 17:16



Needs to be upgraded!

Quick explanation of how to solve (lots of pictures for step by step solutions):

Solving the nonogram gives us the layout of the sudoku, with red and blue squares.

The riddle tells us to replace the red with ‘X’ and blue with ‘V’. This gives us a ‘XV’ sudoku, which can then be solved.

Taking the yellow letters, and replacing a C with an M from the initials, gives an anagram of ‘coffee machine’. The initials also stand for this final answer!

Solution to the nonogram:

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Start by simply filling in rows with large numbers that fill the whole row/column...


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Aha! A pattern! This makes it much easier, the next to fill in now all fill the whole row/column too, just a bit more obscurely...


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And finally, using the pattern, we can finish off the remaining rows/columns.

The riddle:

Crosses are ‘X’ and the V is in bold. These are Roman numerals. So, X is red and V is blue:

The red squares = 10 and the blue (violet) squares = 5


There are 9 white squares in the not full rows/columns. The black lines actually represent the grid lines in the sudoku. And the red/blue is always in between two whites. So adding to the sudoku, we can put Xs and Vs on the grid where the numbers either side sum to the number 10 or 5:

![enter image description here

Solving the new sudoku:

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Using the X and V summations, we can start to fill in some numbers. Note that numbers either side of a V can only be 1, 2, 3 or 4...


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The yellow in the bottom left must be a 3 as a 4 would create two 6s in the row above. This allows us to complete the bottom left square...


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The yellow on the left must be a 1 as a 4 would create two 9s in the left most column. We can now complete another square...


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The top left can be almost completed, as swapping the top two numbers in each column would not work so this is the only possible configuration. The number in the middle top right can only 4 as 1, 2 and 3 don’t work...


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Top middle, top left must be a 3 which means the entire left hand side can now be completed...


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The middle row can now be filled as there are enough numbers to solve like a normal sudoku...


![enter image description here
The left of the V in the top right must be a 4, which allows us to fill in this square...

And from there we can fill in the rest as a normal sudoku:

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Reading off the yellow letters gives


The initials are also important. They tell us to

Replace one of the ‘C’s with an ‘M’. The initials are also the initials of the final answer.

After doing this, we get an anagram (credit Zimonze) of

Coffee machine!

  • $\begingroup$ Your picture does indeed have an error, beside the already-placed 8. $\endgroup$ – Zimonze Apr 13 '20 at 2:10
  • $\begingroup$ @Zimonze thanks!! I was getting muddled adding them in :) $\endgroup$ – Beastly Gerbil Apr 13 '20 at 2:11
  • $\begingroup$ Nice job! If truth be told, my intention was that the 1 and 3 were seen as connected, giving 13, without any clue needed for that. The CM was only intended as a clue for the final answer.. But I like how you interpreted the CM to mean more than that! Well done! $\endgroup$ – Jens Apr 13 '20 at 16:52
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    $\begingroup$ @Jens wow it never even crossed my mind that CM stood for coffee machine lmao :P $\endgroup$ – Beastly Gerbil Apr 13 '20 at 16:56

To see how I got here, see Beastly Gerbil's answer.

Continuing from the revelation that

The nonogram and sudoku combine to create a sudoku XV puzzle,

Here is the solved sudoku:

Solved Sudoku

Red squares are Xs, blue ones are Vs, and yellow ones are the same as the original sudoku. (I didn't track my progress for a solve explanation... sorry)

Looking at the yellow squares,

They contain the numbers
3, 8, 5, 14, 1, 6, 5, 15, 9, 1, 5, 3, 3, 6
(Concatenating digits in adjacent boxes)

Which are known to some as the letters
C, H, E, N, A, F, E, O, I, A, E, C, C, F

These letters are almost an anagram of COFFEE MACHINE, which fits the complaint at the start and the initials given at the end, but the closest it gets is COFFEE ACACHINE. because of the M being replaced by AC, I believe a 1 (A) and a 3 (C) were supposed to stick together and create 13 (M) but ended up separating instead.

  • $\begingroup$ Ahhhh that makes sense! I’ve credited you in my answer, good anagramming!! :P $\endgroup$ – Beastly Gerbil Apr 13 '20 at 2:44
  • $\begingroup$ Oh wait, the initials CM clue for the C -> M I missed that entirely $\endgroup$ – Beastly Gerbil Apr 13 '20 at 3:03
  • $\begingroup$ It also clues (unintentionally?) for your and Zimonze’s solutions, funnily enough $\endgroup$ – El-Guest Apr 13 '20 at 3:56
  • $\begingroup$ Good job on the anagram! I was afraid it would be too difficult, but that clearly wasn't the case. I've given the check to Beastly Gerbil as he, afterall, did the majority of the work. $\endgroup$ – Jens Apr 13 '20 at 16:55

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