body {
    background-image: radial-gradient(red,green); height: 1000px; width: 1000px;
}
h1 {
    text-align: center;
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
}
h3 {
    text-align: center;
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
}