Advent of Code - built entirely with Perl! - 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. In this talk, the creator of Advent of Code will give a behind-the-scenes look at what it takes to run a month-long programming event for over 500,000 people.