html,
/*body with a radial gradient*/
body {
    margin: 0;
    padding: 0;
    height: 100vh;
    background: radial-gradient(ellipse 25% 50% at 50% 50%, #0AA1DA 0%, #077DC3 100%);

    display: flex;
    justify-content: center;
    align-items: center;
}

.center {
    margin: 0;
    position: absolute;
    top: 50%;
    left: 50%;
    margin-right: -50%;
    transform: translate(-50%, -50%)
}