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https://gist.github.com/Metaviolet/682c8d3b05a3a01fd598

//First declare breakpoints
$breakpoints: (
  'small':  767px,
  'medium': 992px,
  'large':  1200px
) !default;

/// Mixin to manage responsive breakpoints
/// @author Hugo Giraudel
/// @param {String} $breakpoint - Breakpoint name
/// @require $breakpoints
@mixin respond-to($breakpoint) {
  // If the key exists in the map
  @if map-has-key($breakpoints, $breakpoint) {
    // Prints a media query based on the value
    @media (min-width: map-get($breakpoints, $breakpoint)) {
      @content;
    }
  }
 
  // If the key doesn't exist in the map
  @else {
    @warn "Unfortunately, no value could be retrieved from `#{$breakpoint}`. "
        + "Available breakpoints are: #{map-keys($breakpoints)}.";
  }
}

//Usage

.selector {
  color: red;
  
  @include respond-to('small') {
    color: blue;
  }
}


http://thesassway.com/intermediate/responsive-web-design-in-sass-using-media-queries-in-sass-32