I've been thinking about starting a hashtag on the #Fediverse called #FediPuzzles, inspired by the TV show "The 1% Club".
Anyone can post a #puzzle, #riddle, #logicGame etc of any form (multiple choice, open answer etc) with the #FediPuzzles hashtag for others to guess, or look for others' puzzles to guess themselves! (I'd recommend to CW your answers to avoid spoiling it for others.)
I'll start with this puzzle: What symbol replaces the question marks in this sequence?
99, L9, 89, 69, 0L, ??