Fortnightly Topic Challenges are all water under the bridge now, so we will do something completely different.

What to Do:

If you have an idea for a tag or a theme of any kind to use as a topic challenge, post it as an answer below. (Do note, you can propose anything, not only a tag). Each answer should start with the title of the topic in a markdown heading (## Title ##). Only one suggestion per answer, please. Here is a list of all tags, to help.

At the start of each month, the highest-voted answer to this post will be selected as that month's topic. Starting from today, users can propose their themes or topics. The selected answer will then be deleted to reduce clutter in the list.

After the selection, a new question will automatically be created in this format. An answer will then be posted to that question with links to all the posts in the featured topic in the fortnight.

We'll again keep a list of all the topics.

Happy Puzzling!

The first MTC will start on July 1st, 2022. In the meanwhile, topics will be gathered and voted on.

  • 3
    $\begingroup$ Is this event going ahead? (Asking for a friend...) $\endgroup$
    – Stiv
    Jan 3, 2022 at 23:14
  • $\begingroup$ @Stiv Sorry all, wasn't able to be active here for 6 months. Sure, we could start in July if it's still relevant. Or perhaps a return of the chain puzzles? $\endgroup$ Jun 15, 2022 at 18:44
  • $\begingroup$ Publicise it in TSL and I'm sure people would start contributing once others do. I think July works well for a starting time :) $\endgroup$
    – Stiv
    Jun 15, 2022 at 19:09
  • $\begingroup$ How is this different from Fortnightly Topic Challenges? $\endgroup$
    – melfnt
    Jul 9, 2022 at 7:13
  • 3
    $\begingroup$ @melfnt In no way other than its length. $\endgroup$ Jul 9, 2022 at 7:15
  • $\begingroup$ @LukasRotter ok then, can I copy here some of the topics proposed for the last FTC that were not used due to the lack of activity? $\endgroup$
    – melfnt
    Jul 9, 2022 at 8:50
  • $\begingroup$ @melfnt Sure, go ahead :) $\endgroup$ Jul 9, 2022 at 8:52

7 Answers 7


- Current Topic -

Board games

Create a puzzle about a real world board game. Any board game will do, but I suspect a classic game might do better.

What's a board game?

Almost anything, besides card games, on the sister stack Board & Card Games.

Some ideas:

  • Monopoly themed
  • SlitherLinks and other puzzles in the shape of a board game like Ludo or Solitaire.
  • "How did we get into this state?" Type puzzles that show a game part way through in an unusual state.

Does it have to be just boardgame related?

No! The cluedo board game has a film, feel free to involve that! Puzzles about monopoly could also reference the economics term!

The Chess Piece in the room

There's already a bunch of puzzles, do we want more? Sure, why not? But they might need to do more to standout against the puzzles already on the site.


Cellular Automata

Here's a regular tag that doesn't seem to get much love:

This can involve puzzles about a well-known cellular automaton, like for example Conway's Game of Life, or a cellular automaton you've created on your own!

Get creative! Maybe we need to reverse-engineer something, try to produce a certain output with given starting conditions, or something entirely different! Crossovers are of course allowed and encouraged.

Great examples of puzzles on this site are Game of Life: Kill the Sun, Can you recreate this fractal I randomly made? and Checkerboard Infection

copied from Fortnightly Topic Challenges Threrun: Topic Suggestions originally posted by Lukas Rotter


Game/Quiz Shows

This... is... Puzzling! Let's meet this month's topic challengers...

Create a puzzle themed around a real-life game or quiz show. The puzzle must involve the basic format of the overall show in some way, e.g. a Jeopardy!-themed puzzle might include answering trivia questions chosen from a board, while an Only Connect-themed puzzle might include questions and a .

Some examples on this site, including the game/quiz shows they reference:

And Wikipedia has "Lists of game shows" from a variety of countries, linked here for informational and inspirational purposes.


  • Puzzles that are dressed up as or reference game/quiz shows but do not directly involve the format of a real-life show are not eligible for this challenge, e.g. the Monty Hall problem, a standalone
  • Puzzles asking about optimal strategies for playing game/quiz shows are eligible, as long as what the "best" strategy is can be objectively quantified, e.g. Monopoly Game Show: Is there a winning strategy?

Copied from my submission for the Fortnightly Topic Challenges Threrun (over a year and a half ago... time flies huh?)


Möbius Strips, Klein Bottles, and other unusual topological surfaces

enter image description here

Imagine an elastic square as above. If you ignore the red edges and glue the blue edges so that they have the same orientation, you get a Möbius Strip. If you join both pairs of edges, you get a Klein Bottle. This is not the only interesting surface; you can have 12 different topologies in total by joining two pairs of edges of a square, which include:

enter image description here enter image description here enter image description here

(The last one is a plain torus.) The universal rule is that, if you're on the surface and you walk through an edge, you enter back to the grid through the matching edge with same orientation.

For example, consider this 4x4 grid:

A1 A2 A3 A4
B1 B2 B3 B4
C1 C2 C3 C4
D1 D2 D3 D4

Assume the Klein bottle topology at the top. If you're at B1 and walk left, you end up at B4 (by going through the red parallel edge). If you're at A2 and walk upwards, you end up at D3 (by going through the blue twisted edge).

For the first one on the second image set (the one where the matching edges are adjacent to each other), if you walk upwards from A1, you enter back at A1 but facing right!

The challenge is to create a puzzle that involves an unusual topological surface (which excludes plain wrap-around mechanic a.k.a. cylinder and torus). Such a puzzle may involve tiling, graph, crossword, or a grid-deduction genre, among others.

Some good examples:

You can search for puzzles containing torus, toroidal, or wrap around for some ideas.

There is even a programming language called Klein that can run the same code on different topologies!

copied from Fortnightly Topic Challenges Threrun: Topic Suggestions originally posted by Bubbler


Now in 3D

The tag can bring a nice twist to a variety of puzzle types. We've seen paper folding, grid deduction, crosswords, mazes and even pencil-and-paper game puzzles use the extra dimension to great effect. While presenting 3D things in a 2D environment brings some challenges to both setters and solvers, the added dimension offers a nice opportunity to produce some real mind benders when done right. Creativity is encouraged – the only requirement here is that the puzzle somehow make use of three-dimensional space.


mobile-friendly puzzles

Why is this post so badly formatted you may ask? Well it's because I am dictating into a mobile phone.

a lot of us are busy and on the go these days and don't have time to sit at the computer and solve puzzles but we'd still love to have some fun. I propose for the monthly topic challenge mobile friendly puzzles. These are puzzles which can easily be solved on your mobile phone using common knowledge or perhaps looking up a few things, but not poring over complicated charts or graphs, using Excel, filling out drawings, or requiring extensive markup or time writing out a beautifully formatted entry.
Creating a good mobile-friendly puzzle is a true challenge for a Puzzle Master for they must create a puzzle that is simple enough to be viewed and solved on a mobile device and yet elegant, interesting, and unique. It should be answerable in a few lines of text or perhaps by uploading a simple screenshot with minimal markup.
There are plenty of examples on this site; here's one at random: It's a... Ohh... puzzle (BpFp)

In the spirit of this being a Challenge, entries should be innovative and new in some way, to the op's knowledge. For example:
-Something that looks like an affix-riddle or What is a Word, but is actually something else entirely, or takes a new or unexpected twist.
-A puzzle with a visual component leveraging a never seen before mechanism.


Variety Slitherlinks

The challenge is to create a puzzle that shows an original perspective on the basic slitherlink puzzle.

It could have:

  • slightly altered rules (why not 2 loops instead of 1?)
  • a non-standard grid (hexagonal? non-2D?)
  • show clues in a way one wouldn't expect
  • combine multiple slitherlinks in one grid
  • combine slitherlink rules with other grid-deduction puzzle types
  • hide some encrypted information that the puzzler should decode
  • any other enigmatic twist that you can think of

I've created a Slitherlink with a message before, and I like the originality of Rhombicosidodecahedron Slitherlink and 9x9 Sudoku Slitherlink Hybrid.


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