Generated by SassMeister.com.

SassMeister-input.scss

// ----
// libsass (v3.2.5)
// ----

$tablet: 786px;
$desktop: 1024px;
$desktopwide: 1200px;

$font-sizes: (
  null: 14px,
  $tablet: 20px,
  $desktop: 25px
);

@mixin font-size($fs-map) {
  @each $fs-breakpoint, $fs-font-size in $fs-map {
    @if $fs-breakpoint == null {
      font-size: $fs-font-size;
    }
    @else {
      @media screen and (min-width: $fs-breakpoint) {
        font-size: $fs-font-size;
      }
    }
  }
}

.section {
  @include font-size($font-sizes);
}

SassMeister-output.css

.section {
  font-size: 14px;
}

@media screen and (min-width: 786px) {
  .section {
    font-size: 20px;
  }
}

@media screen and (min-width: 1024px) {
  .section {
    font-size: 25px;
  }
}