a precess production

precess-input-1412093725.scss

.shape{
  border:5px solid red;
}

.square{
  @extend .shape;
  width:100px;
  height:100px;
}

.circle{
   border-radius:100%;
   @extend .square;
}  

precess-output-1412093725.css

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

.square, .circle {
  width: 100px;
  height: 100px;
}

.circle {
  border-radius: 100%;
}