@mixin has-parent($parent) {
  @if (str-index($parent, '.') or str-index($parent, '#')) {
    #{$parent} & {
      @content;
    }
  } @else {
    .#{$parent} & {
      @content;
    }
  }
}

@mixin limit($rules) {
  margin: auto;
  @each $rule, $width in $rules {
    @include media($rule) {
      max-width: $width;
    }
  }
}