* {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

.nav-bar {
    width: 100%;
    background-color: #333;
    overflow: hidden;
    position: fixed;
    top: -42px;
    transition: top 0.3s
}

.nav-bar a {
    color: #fff;
    padding: 10px;
    display: inline-block;
    text-decoration: none;
}

.nav-bar a:hover {
    background-color: #0081cb;
}

.main {
    padding: 20px;
    height: 2000px;
}