Responsive SASS: Chain media queries and coordinate named breakpoints

responsive.scss

// Created by Max Luster (@maxluster)
// Usage instructions at https://bugsnag.com/blog/responsive-typography-with-chained-media-queries
// Requires SASS >= 3.3
// Enhanced by Breakpoint 2.4.x and Compass 1.0 (alpha)
// For SASS 3.2.x support, use https://gist.github.com/maxluster/c9ecc6e4a6770e507c2c

// Provides a simplified syntax for chaining media queries across named or numeric breakpoints
@mixin responsive($properties, $default-value, $responsive-values){

  // No named breakpoints by default
  $named-breakpoints: () !default;

  // Apply default property values
  @each $property in $properties{
    #{$property}: #{$default-value};
  }
  
  @each $breakpoint, $value in $responsive-values{

    // Get named breakpoint values
    @if type-of($breakpoint) == string{
      @if(map-has-key($named-breakpoints, $breakpoint)){
        $breakpoint: map-get($named-breakpoints, $breakpoint);
      }
      @else{
        @warn "Couldn't find named breakpoint: " + $breakpoint;
      }
    }

    // Use Breakpoint if it exists
    @if mixin-exists("breakpoint"){
      // Apply at breakpoint
      @include breakpoint($breakpoint) {
        @each $property in $properties{
          #{$property}: #{$value};
        }
      }
    }
    // Fallback to min-width media queries
    @else{
      @media screen and (min-width: $breakpoint) {
        @each $property in $properties{
          #{$property}: #{$value};
        }
      }
    }

  }

}

// Extras!

// Use $named-breakpoints with block-style media queries
@mixin named-breakpoint($breakpoint){

  @if type-of($breakpoint) == string{
    @if(map-has-key($named-breakpoints, $breakpoint)){
      $breakpoint: map-get($named-breakpoints, $breakpoint);
      @if mixin-exists("breakpoint"){
        @include breakpoint($breakpoint){
          @content;
        }
      }
      @else{
        @media screen and (min-width: $breakpoint) {
          @content;
        }
      }
    }
    @else{
      @warn "Couldn't find named breakpoint: " + $breakpoint;
    }
  }

}

// Create a scope for a local set of named breakpoints
@mixin with-named-breakpoints($context-breakpoints){
  $old: $named-breakpoints;
  $named-breakpoints:  map-merge($named-breakpoints, $context-breakpoints) !global;
  @content;
  $named-breakpoints: $old !global;
}

Thanks! This gist and its accompanying post came really handy. It's unbelievable that practical solutions like this one aren't the norm today...

I wrote a small function to automatically scale a value for each width in the $named-breakpoints map given a base width.

@include responsive("font-size", $base-font-size + px, resp-scale($base-width, $base-font-size));

The cool thing is that if your typography settings are all in rem then the above @include is all you need to scale everything to any width!

Have someone got this to work with libsass? i'm getting:
[gulp-sass] source string:40: error: error reading values after 600px