JSFiddle - React, Tailwind, and code Playground

HTML

<div></div>
<div opacity></div>

CSS

div {
  border: 1px solid;
  background: yellow;
}
div[opacity] {
  opacity: .99;
}
div::after {
  content: 'You should only see this text if the <div> creates a stacking context.';
  position: relative;
  z-index: -1;
}