/**
  * 浏览器适配
  *
  * xs:
  * sm:   < 1280
  * md:   1280 - 1440
  * lg:   1440
  */
@mixin mq($breakpoint) {
    $mq-sm: "(max-width: 1280px)";
    $mq-md: "(min-width: 1280px) and (max-width: 1440px)";
    $mq-lg: "(min-width: 1440px)";

    
    @if $breakpoint == sm {
        @media #{$mq-sm} { @content; }
    } 
    @else if $breakpoint == md {
        @media #{$mq-md}  { @content; }
    } 
    @else if $breakpoint == lg {
        @media #{$mq-lg} { @content; }
    }
}