dynamic font size with sass and media query

font-big.scss

/*
 https://gist.github.com/honsa/98c25b18b773e2944e32a2f3fdc9a9d7
*/

@mixin font-big($additionalValue: 0%, $op: '+') {

  @if($op == '+'){
    font-size: calc(60px + #{$additionalValue});
  } @else {
    font-size: calc(60px - #{$additionalValue});
  }

  @media (max-width: 999px) {
    @if($op == '+'){
      font-size: calc(52px + #{$additionalValue});
    }@else {
      font-size: calc(52px - #{$additionalValue});
    }
  }

  @media (max-width: 767px) {
    @if($op == '+'){
      font-size: calc(42px + #{$additionalValue});
    }@else {
      font-size: calc(42px - #{$additionalValue});
    }
  }

  @media (max-width: 414px) {
    @if($op == '+'){
      font-size: calc(36px + #{$additionalValue});
    }@else {
      font-size: calc(36px - #{$additionalValue});
    }
  }

  @media (max-width: 320px) {
    @if($op == '+'){
      font-size: calc(24px + #{$additionalValue});
    }@else {
      font-size: calc(24px - #{$additionalValue});
    }
  }
}