Below is a list of all puzzles posted as part of the Puzzling Advent Calendar 2021:
La laa laaaaaa laa la Christmas by Stiv
A Christmas Tree for broke Nerds by Lukas Rotter
Tentai Show by Jafe
Decorating with Ingrid Deduction by Jeremy Dover
Christmas Shopping by Lypyrhythm
Naughty or Nice? by Lukas Rotter
Don't forget the lyrics! by Stiv
At the end of the ...
Prove that $\pi$ is greater then 3 by Florian F
To me this is an example of great mathematical elegance. It seems obvious that such a geometric proof is possible but actually finding a cut of the three squares is still non trivial. Both highly upvoted answers are excellent. One can easily run into some messy algebra to see whether a proposed solution ...
Decipher this message for instructions to decipher this message by SlowMagic
This was a wonder. It must have took time to find words with the same restrictions as the puzzle needed. The way it was solved, by working backwards, kind of gives everyone the feeling that the answer needs to be known before you can solve it. The comment in M Oehm's beautifully ...
Definition Resolution by noneuclideanisms
This puzzle hardly flew under the radar, since both the puzzle and the solution were both very well received...indeed, it tops the "most popular" list selected algorithmically. And rightly so.
It has an enigmatic presentation, but is approachable. The differing fonts of the words in the puzzle tantalized, ...
Throwing a purely tag-based one in...
Games meant to be played with a pencil and paper tend to be simple little time wasters. But that doesn't mean they can't be incorporated into puzzles in interesting ways! Their very simplicity means puzzles with them can still be easily understandable/accessible even if a little more complex.
Restricted Title: xkcd 1xxx
See this FTC, which dealt with the first 1000 xkcd comics
Usually the title is decided upon later in the puzzle creation process, chosen to be fitting and often to provide a hint/reference. Here we're going to go the other way.
Below is a list of the titles for xkcd comics 1000-1999, filtered down to those titles which are a valid ...
Create a puzzle where the first step is a nonogram whose solution reveals further steps that must be taken. Crucially, the full puzzle is entirely self-contained within the nonogram and flavour text. (i.e. Not just using a nonogram as the first step in a long string of grid-deduction puzzles which require additional grids to be displayed in ...
First of all, if all you want is our actual policy then
you can find it in this question:
Proposed policy on mathematical questions
The policy described there is, briefly:
A question is off-topic on Puzzling if it is routine.
This means that the question can be answered by following a standard procedure.
Other related considerations: is the ...
Just found this meta post, so just to chip in with my original thinking when writing that close reason:
if it were any other site on the internet where an earlier version of the puzzle were found without being attributed, it would be closed using the canned response:
This looks like a puzzle you found elsewhere. For content you did not create yourself, ...