<style contenteditable> style {
  background-color: white;
  border-radius:3px;
  box-shadow:
    0 5px 15px rgba(0,0,0,0.20),
    0 5px 15px rgba(0,0,0,0.30);
  color:#333;
  display: block;
  font-size: 20px;
  line-height 28px;
  margin: auto;
  overflow:auto;
  padding: 18px;
  max-width: 800px;
  white-space: pre; 
}

style:before {
  content:"Edit the style!";
  border-bottom:2px solid grey;
  display:block;
  font-size:36px;
  font-weight:bold;
  margin-bottom:18px;
  padding-bottom:18px;
}
  
style:focus {
  outline:none;
}

body {
  background:grey;
  margin: 0;
  padding: 10px;
}
  
*, *:before {
  box-sizing:border-box;
  transition:all .2s ease-out;
}
</style>
Rerun