.copy-btn {
    display: none;
    float: right;
    position: absolute;
    color: white;
    border: solid 1px white;
    z-index: 1000;
    top: 5px;
    right: 5px;
    cursor: pointer;
}

.viewer-code {
    position: relative;
}

code:hover + .copy-btn, .copy-btn.hover {
    display: inline-block;
}

code {
    overflow: hidden;
    position: relative;
}