style.css

* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    scroll-behavior: smooth;
    text-decoration: none;
}

body {
    min-height: 100vh;
    font-family: sans-serif;
}

nav {
    display: flex;
    justify-content: space-between;
    position: fixed;
    top: 0;
    left: 0;
    height: 75px;
    width: 100%;
    align-items: center;
    background: #000;
    transition: .6s;
    z-index: 99;
    box-shadow: 4px 4px 10px rgba(0, 0, 0, 0.16);
}

.navbar-brand {
    font-size: 1.9rem;
    margin-left: 20px;
    color: #fff;
}

nav ul {
    position: relative;
    display: flex;
    align-items: center;
    justify-content: center;
    margin-right: 20px;
}

nav ul li {
    position: relative;
    list-style: none;
    margin: 0px 5px;
}

nav ul li a {
    position: relative;
    text-decoration: none;
    font-size: 1.2rem;
    color: #fff;
    padding: 0px 5px 5px;
    transition: .6s;
}

nav ul li a:hover {
    color: #f1f1f1;
}

.active {
    border-bottom: 2px solid royalblue;
    color: royalblue;
}

section {
    min-height: 110vh;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 5rem;
}

section:nth-child(odd) {
    background: burlywood;
}