html,
body {
    height: 100%
}

body {
    display: flex;
    align-items: center;
    background-color: #9a9a9a;
}

.container {
    max-width: 500px;
    margin: 0 auto;
    padding: 50px;
    background-color: rgb(208, 208, 208);
    box-shadow: 0 0 24px 0 rgba(116, 116, 116, 0.06), 0 1px 0 0 rgba(0, 0, 0, 0.02);
}

.background {
    position: absolute;
    top: 0;
    bottom: 0;
    left: 0;
    right: 0;
    z-index: -1;
}