Mixin to use in SCSS

_mixins.scss

@mixin mobile($max-w : $mobile) {
  @media (max-width: $max-w) {
    @content;
  }
}

@mixin tablet($max-w : $tablet) {
  @media (max-width: $max-w) {
    @content;
  }
}

@mixin desktop($max-w : $desktop) {
  @media (min-width: $max-w) {
    @content;
  }
}