title: Using media breakpoints in Bootstrap 4-alpha
body: <p>In Bootstrap 3 I use this:</p>
  
  <pre><code>.something {
      padding: 5px;
      @media screen and (min-width: $screen-sm-min) { 
          padding: 20px;
      }
      @media screen and (min-width: $screen-md-min) { 
          padding: 40px;
      }
  }
  </code></pre>
  
  <p>How can I do the same thing in Boostrap 4-alpha? I can't find an example in their docs. 
  This is in  variables.scss</p>
  
  <pre><code>$grid-breakpoints: (
    xs: 0,
    sm: 576px,
    md: 768px,
    lg: 992px,
    xl: 1200px
  ) !default;
  @include _assert-ascending($grid-breakpoints, "$grid-breakpoints");
  @include _assert-starts-at-zero($grid-breakpoints);
  </code></pre>