This is a Lua (5.4.0) implementation of this year's Advent of Code.
You'll need a working Lua installation: you can build it yourself with a working C compiler, or download a pre-built binary if you don't want to bother with building it.
Each day has a directory of its own and generally has an input file (eg. input.txt) and a main file (eg. main.lua) that Lua has to run (eg. lua main.lua).
Advent of Code is an Advent calendar of small programming puzzles for a variety of skill sets and skill levels that can be solved in any programming language you like. People use them as a speed contest, interview prep, company training, university coursework, practice problems, or to challenge each other.
Lua is a powerful, efficient, lightweight, embeddable scripting language. It supports procedural programming, object-oriented programming, functional programming, data-driven programming, and data description.