main-style.css

body {
    background-image: url('background1.jpg');
    background-repeat: no-repeat;
    background-attachment: fixed;
    background-size: cover;
    margin: 0;
    padding: 0;
    color: white;
    font-family: Arial, Helvetica, sans-serif;
    width: 100%;
    overflow-x: hidden;
}

.header {
    display: flex;
    justify-content: center;
}

nav {
    margin: 0;
    padding: 0;
}

.nav-ul {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin: auto;
    padding: 0;
    background-color: rgb(49, 0, 84);
    border: solid greenyellow;
    border-style: outset;
    border-width: 1px;
}

.nav-list {
    display: inline-block;
    text-align: center;
    font-size: 90%;
    background-color:indigo;
    border: solid;
    border-style: inset;
    border-color: #48255c;
    border-width: 2px;
    border-radius: 10%;
    width: 20%;
}

footer {
    text-align: center;
    margin-top: 30%;
}

a {
    color: white;
    transition: all .15s;
}

a:hover {
    opacity: 80%;
    text-decoration: none;
}