mixin.scss

@mixin responsive($media) {
  @if $media == sm {
    @media (min-width: 768px) { @content; }
  }
  @else if $media == md {
    @media (min-width: 992px) { @content; }
  }
  @else if $media == lg {
    @media (min-width: 1200px) { @content; }
  }
}