.copy-button {
  position: absolute;
  top: .4rem;
  right: .4rem;
  padding: .25rem .5rem;
  font-size: .8em;
  color: #ccc;
  background: #1c1e22;
  border: 1px solid #333;
  border-radius: .25rem;
  cursor: pointer;
  opacity: 0;
  transition: opacity .2s ease;
}

pre:hover .copy-button {
  opacity: 1;
}

.copy-button:hover {
  color: #fff;
  border-color: #555;
  background: #222;
}