JSFiddle - React, Tailwind, and code Playground

HTML

<div class="panel">base</div>
<div class="panel--rounded">dsaf</div>
<div class="panel--spacy">extra spacy</div>
<div class="panel--rounded panel--spacy">extra spacy + rounded</div>

SCSS

.panel {
  background : #eee;
  border     : 1px solid #888;
  display    : block;
  padding    : 20px;
  
  &--rounded{
    @extend .panel;
    border-radius: 20px;
  }
  
  &--spacy {
    @extend .panel;
    padding : 40px;
  }
}