a precess production

precess-input-1412094466.scss

.shape{
  border:5px solid red;
}

@mixin size( $dimensions ){
  height:$dimensions;
  width:$dimensions;
}

.square{
  @extend .shape;
  @include size( 50% );
}

.circle{
   border-radius:100%;
   @include size( 150% );
}  

precess-output-1412094466.css

.shape, .square {
  border: 5px solid red;
}

.square {
  height: 50%;
  width: 50%;
}

.circle {
  border-radius: 100%;
  height: 150%;
  width: 150%;
}