Never knew of Advent of Code until today. I'm quite late but still started giving it a go and I'm loving it! 4 stars so far :)
I'm using dart to try and get familiar with the language so I'm slow as anything but I find great fun in trying to solve each little logic puzzle.
Fosstodon is an English speaking Mastodon instance that is open to anyone who is interested in technology; particularly free & open source software.