h1 { text-align: center; }
pre {
    border: 1px solid #ccc;
    box-shadow: 3px 3px 3px #eee;
    padding: 8pt;
    font-family: monospace;
    overflow: auto;
    margin: 1.2em;
}
pre code {
    position: relative;
    overflow: visible;
    padding-top: 1.2em;
}
pre code:before {
    display: none;
    position: absolute;
    background-color: white;
    top: -10px;
    right: 10px;
    padding: 3px;
    border: 1px solid black;
}
pre code:hover:before { display: inline; }