#box {
    width: 100%;
    height: 100%;
    background-color: #f7fafc;
    background-image: url(./hdk-login-bg.jpg);
    background-size: cover;
    background-position: 50% 50%;
    background-repeat: no-repeat;
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    z-index: 1;
}

.container {
    position: absolute;
    z-index: 2;
    left: 50%;
    top: 50%;
    transform: translate(-50%, -50%);
}