nav {
    position: fixed;
    top: 0;
    left: 0;
    width: 14em;
    height: 100vh;
    background: #f7f7fa;
    border-right: 1px solid #ddd;
    padding: 2em 1em 1em 1em;
    box-sizing: border-box;
    overflow-y: auto;
    z-index: 100;
}

nav ol {
    list-style: none;
    padding: 0;
    margin: 0;
}

nav ol li {
    margin-bottom: 1em;
}

nav ol li a {
    display: block;
    color: #222;
    text-decoration: none;
    padding: 0.5em 0.75em;
    border-radius: 4px;
    transition: background 0.2s;
}

nav ol li a:hover,
nav ol li a:focus {
    background: #e0e0f0;
    color: #000;
}

/* Add left margin to main content to avoid overlap */
header,
div.main {
    margin-left: 16em;
}