header {
    text-align: center;
}
nav ul {
    list-style-type: none;
    background-color: black;
    margin: 0;
    display: flex;
    justify-content: center;
}

nav ul li {
    padding: 1vw 2.5vw;
}

nav ul li a {
    text-decoration: none;
    color: white;
    font-size: 3vw;
}

nav ul li a:hover {
    color: blue;
}