Heading with fluid font-size

25px

150px

#top .av-special-heading.fluid-font .av-special-heading-tag {
  font-size: min(max(25px, calc(1.5625rem + ((1vw - 3.2px) * 10.5042))), 150px);
  min-height: 0vw;
}

Hello

see: https://websemantics.uk/tools/responsive-font-calculator/

Default Style

Modern Style