Here are three simple lines of code to smooth sizing the root font size depends on the screen size.
:root {
font-size: calc(1rem + 0.25vw);
}You can also use 'clamp' to use the smooth sizing only between 380px and 1240px:
:root {
--fluid-16-20: clamp(1rem, 0.8895rem + 0.4651vi, 1.25rem);
}