Generated by SassMeister.com.

SassMeister-input.scss

// ----
// Sass (v3.3.5)
// Compass (v1.0.0.alpha.18)
// ----

// Define items

$brand-default: (
  'color': #999,
  'font-size': 1em
);

$brand-bright: map-merge($brand-default, (
  'name': bright,
  'color': yellow
));

$brand-dark: map-merge($brand-default, (
  'name': dark,
  'color': black,
  'font-size': 2em
));

// Create collection from items
$brands: (
  $brand-default,
  $brand-bright,
  $brand-dark,
);

// Variant Mixin

@mixin brand-variant ($map) {
  
  // Build the selector
  $selector: '.brand';
  @if(map-has-key($map, 'name')) {
    $selector: #{$selector}--#{map-get($map, 'name')};
  }
  
  // Define the selector's styles
  #{$selector} {
    h3 {
      font-size: map-get($map, 'font-size');
      color: map-get($map, 'color');
    }
  } 
}

// Loop over items, passing the value map as the parameter
@each $item in $brands {
  @include brand-variant($item);
}

SassMeister-output.css

.brand h3 {
  font-size: 1em;
  color: #999999;
}

.brand--bright h3 {
  font-size: 1em;
  color: yellow;
}

.brand--dark h3 {
  font-size: 2em;
  color: black;
}