An (in)famous code challenge in computer graphics is to write a complete ray tracer small enough to fit onto a business card. I've really enjoyed reading through some of the submissions over the years (e.g. 1, 2, 3, 4), and I've wondered what a chemistry-specific equivalent might be. As a first step in this space—and as a learning exercise for myself as I try to learn C++—I decided to try and write a tiny Lennard–Jones simulation.