Grant Sanderson (of 3Blue1Brown fame) nerd-sniped me many years ago with a video about what happens when you try to visualise a fourier series applied to $e^{i\pi}$.
I ended up writing a little project in Rust that takes in SVG (with some caveats), and produces and visualisation like shown in the video using SDL and used this project as part of my personal statement when applying for university. The project wasn’t in a working state when I actually submitted my application, and I ended up cramming it into a functional state when I realised I had interviews where they might ask me about it! I later added a brief blog post to this website about it. You can see the sample output below.
This was one of those projects I always felt I should revisit, so I’m currently working on a brand new web version! It’s not ready yet but I’ll link it here as soon as it is.