Using Susy (http://susy.oddbird.net/) with @extend rather than @include

_grid.scss

// Imports -------------------------------------------------------------------

@import "susy";

// Configuration -------------------------------------------------------------

$total-cols             : 12;
$col-width              : 4em;
$gutter-width           : 1em;
$side-gutter-width      : $gutter-width;

$show-grid-backgrounds  : true;

/* Grid ------------------------------------------------------------------- */

.container {
  @include container;
  @if $show-grid-backgrounds {
    @include susy-grid-background;
  }
}

.column {
  @include float(left);
}

@for $context from 1 through $total-cols {

  /* Non-nested grids */
  .grid-#{$context} {
    @extend .column;
    margin-right: gutter();
    width: columns($context);
  }

  .prefix-#{$context} {
    @include prefix($context);
  }

  .suffix-#{$context} {
    @include suffix($context);
  }


  /* Nested grids */
  .column-context-#{$context} {
    @extend .column;
    margin-right: gutter($context);
  }

  @for $cols from 1 through ($context - 1) {
    .grid-#{$cols}-of-#{$context} {
      @extend .column-context-#{$context};
      width: columns($cols, $context);
    }
    .prefix-#{$cols}-of-#{$context} {
      @include prefix($cols, $context);
    }
    .suffix-#{$cols}-of-#{$context} {
      @include suffix($cols, $context);
    }
  }

}

.alpha {
  @include alpha;
}

.omega {
  @include omega;
}

.omega-nested {
  @extend .omega;
  margin-right: 0;
}

.full-nested {
  @include full($nested: true);
}

.full {
  @extend .full-nested;
  margin: {
   left: side-gutter();
   right: side-gutter();
  }
}