Unanswered Questions
459 questions with no upvoted or accepted answers
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Unsolved Mysteries: D'Agapeyeff cipher
The D'Agapeyeff cipher is an as-yet unbroken cipher that appears in the first edition of "Codes and Ciphers", an elementary book on cryptography published by the cryptographer Alexander D'...
- 3,081
37
votes
0
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Noita Eye Glyphs
A puzzle found hidden between the background layers of the computer game Noita. The puzzle has not been solved since it was added to the game in October of 2020.
It is made of thousands of eye images, ...
- 7,254
27
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0
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Is there a move-efficient way to rotate the center pieces on the Octo-Star?
I'm looking for a more efficient algorithm to rotate the center column of the Octo-Star puzzle 45 degrees.
The situation below occurs when four properly-oriented edges are next to each other, ...
- 61
26
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3k
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Decrypting the Key: "Phage is Spreading.."
I've been trying to solve this puzzle called "Phage is Spreading.."
...
- 13.4k
22
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0
answers
2k
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REALLY important days in history
@Z. Dailey asks a mathematical puzzle Important days in history... and to come! with a series of dates in years 1973, 1978, 1983, 1992, 2005.
My puzzle asks the question: What is the previous date in ...
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20
votes
0
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1k
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Alternate, complex potions puzzle from HP fanfic
A long narrow room. The entrance is blocked by purple flame, the path onward blocked by black flame. On a table, the only thing in the room, are two dozen potions in opaque bottles. Half green glass, ...
- 201
19
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0
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638
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Edge Removal Game
There is a complete undirected graph with n nodes (n > 1). Alice and Bob take turns removing one edge from the graph, with Alice going first. The player whose move causes any node to become ...
- 5,192
19
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0
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896
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Determining the meaning of a challenge coin
I saw this rather cool looking challenge coin the other day, and I was wondering what the associated binary on the back of it means, as it isn't standard ASCII.
In plaintext:
...
- 13.4k
15
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0
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1k
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PSE Advent Calendar 2025 (Day 16): A TANtastic gift
This puzzle is part of the Puzzling Stack Exchange Advent Calendar 2025. The accepted answer to this question will be awarded a bounty worth 50 reputation.< Previous Door Next Door >
You wake up ...
- 780
15
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0
answers
3k
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Crack the pigeon code
Can you crack this message? It was discovered in a chimney in 2012 attached to a carrier pigeon and was most likely sent during the D-day invasions. The GCHQ was not able to crack it, even after ...
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15
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0
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2k
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14
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732
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Qubes: Oh, For the Love Of
TL;DR: This is a mixture between a tribute/spin-off puzzle and an attempt at a new puzzle type, greatly inspired by the notorious arcade game, Q*bert, published originally by Gottlieb Amusement Games. ...
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14
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0
answers
991
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Grandma's keynote
Found this note which is addressed
To my grandma, in her chest
Since she's passed now, here's my quest..
What tickled her interest?
And who invited her as guest?
- 123
14
votes
1
answer
728
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An endless succession of harmless checks
Similarly to my previous chess instalment, this puzzle continues to explore the underlying geometry to be found in a sequence of consecutive checks. This time however, we will ditch the limiting ...
CommunityBot
- 1
13
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0
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444
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origamidevil.png
This is an optimized version of Wordless Translation. Chinese is now irrelevant. This solves to a clear thematic phrase.
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