I remember seeing at least one other community related to this, which had regular math problems.
What I'm thinking is having a general community for any of the following:
joke style riddles
more complex riddles (ex. missing dollar riddle)
math problems (geometry, infinite doors, monty hall)
optical illusions
those physics 'what would happen' questions (ex. which bucket would fill first, which way would the balloon move)
Keeping it open would allow for more content, and it will also keep things fresh, since having the same type of question every day might get boring for users.
What should the community be called? Some ideas so far:
riddler: might be too specific to the character, or the concept or riddles
???: I thought this was fun, but it might cause issues with other fediverse platforms
what: Not as fun, but solves the issue above
What instance should the community be on?
Any best practices? We could have tags for the approximate difficulty of the questi