This was my first Advent of Code, and I used it to learn and practice Elixir!
I wrote and ran the first ~17 days or so as scripts, and then to take advantage of mix packages I turned it into a proper project where each day is a module. Debugging Intcode programs with an actual elixir shell was much easier, so I'm glad I made that transition and will start next year's AOC with a proper project structure!
$ iex -S mix
iex> Aoc2019.Day25.p1
I found Day 18 the most challenging - learning to write a few different versions of BFS and performing multiple rounds of optimizations to solve the puzzle in a reasonable amount of time was a lot of fun!