button.rustc-copy {
    display: none;

    margin: 0.15rem;
    padding: 0.35rem 1.2rem;
    border: 1px solid #DDD;
    border-radius: 3px;
    text-align: center;
    font-size: initial;
}

div.code-block:hover > button.rustc-copy, button.rustc-copy:hover {
    display: inline-block;

    position: absolute;
    top: 0.5rem;
    right: 0.5rem;

    opacity: 0.7;
}

pre.rustc-source {
    display: none;
}
