Advent of code 2021 solutions in vimscript because apparently I enjoy pain.
To run a given day's solution, use ./run.vim {day}.
To get started working on a given day, use ./run.vim -s {day} (downloads
input file and creates template for solution file). Make sure you have stored
your advent of code session cookie in a file called session_cookie in this
repository. Don't commit it obviously (it's in the gitignore for a reason).