nav {
    background-color: #333;
    padding: 1em;
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    z-index: 1000;
}

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

nav li {
    display: inline;
    margin-right: 20px;
}

nav li:last-child {
    margin-right: 0;
}

nav a {
    color: #fff;
    text-decoration: none;
    font-size: 16px;
}

nav a:hover {
    color: #ddd;
}

/* 為了避免導航欄覆蓋內容 */
body {
    margin-top: 60px;
}