src: https://medium.com/developing-with-sass/creating-a-dead-simple-sass-mixin-to-handle-responsive-breakpoints-889927b37740

_simple-breakpoint-mixin.scss

@mixin breakpoint($class) {
  @if $class == xs {
    @media (max-width: 767px) { @content; }
  }
 
  @else if $class == sm {
    @media (min-width: 768px) { @content; }
  }
 
  @else if $class == md {
    @media (min-width: 992px) { @content; }
  }
 
  @else if $class == lg {
    @media (min-width: 1200px) { @content; }
  }
 
  @else {
    @warn "Breakpoint mixin supports: xs, sm, md, lg";
  }
}