Fixed font sizes need a breakpoint for every screen width. Fluid sizes grow between a minimum and a maximum, so a display headline is large on a desktop and still fits on a phone.
Where fluid type stops
Body text should not shrink below a comfortable size, and long headlines need a maximum, or they take over the first screen. Leitvia sets both ends for every step of its scale, from meta text to display.
Resize the window on the showcase and watch the headline: it changes size smoothly and never wraps word by word.