Fluid typography is pretty amazing. We have a writeup of how it all works. But as fancy as that is, it's still scaling the type linearly. What if we wanted the type size to fall along a curve? The math gets a bunch more complicated, but it's possible.
Jake Wilson digs in, and while he finds that calc() isn't quite up for the job (e.g. font-size: calc(3vw * 3vw); /* This doesn't work in CSS */), he does land on a technique he's calling Poly Fluid Sizing, which takes a map of breakpoints and font sizes and linear interpolates them just about as good (*it depends*).