style.css

.code-copy {
  color: #aaa;
  display: inline-block;
  cursor: pointer;
}

.code-copy::after {
  position: absolute;
  right: calc(100% + 8px);
  background: #424242e5;
}

.code-copy._suc::after {
  content: "Content Copied!";
  opacity: 0; /* for animation to work */
  animation: fadeout 3s;
}

.code-copy._err::after {
  content: "Oops, an error occurred!";
  opacity: 0; /* for animation to work */
  animation: fadeout 3s;
}

div[class*="language-"] pre .code-copy {
  position: absolute;
  z-index: 1000;
  top: 35px;
  right: 5px;
  width: 24px;
  height: 30px;
  background: no-repeat url('./copy.svg');
  opacity: 0;
}

div[class*="language-"] pre:hover .code-copy {
  opacity: 1;
}

.content pre, .content pre[class*=language-] {
    overflow-y: hidden;
}

@keyframes fadeout {
  0% {
    opacity: 1;
  }
  100% {
    opacity: 0;
  }
}