.codeblock {
    position: relative;
}
.codeblock pre {
    margin: 0;
}
.copy-btn {
    position: absolute;
    top: .5rem;
    right: .5rem;
    padding: .25rem .5rem;
    font-size: .8rem;
    border: 1px solid rgba(0,0,0,.1);
    border-radius: .25rem;
    background: rgba(255,255,255,.8);
    cursor: pointer;
}
.copy-btn:hover { background: #fff; }
.copy-ok { background: #e6ffed; border-color: #b7ebc6; }
.copy-fail { background: #ffecec; border-color: #ffb3b3; }