.copy-btn{position:absolute;top:0.5rem;right:0.5rem;padding:0.25rem 0.6rem;font-size:0.75rem;background:rgba(0,0,0,0.4);color:#fff;border:none;border-radius:2px;cursor:pointer;opacity:0;transition:opacity 0.2s;}pre:hover .copy-btn{opacity:1;}