body {
    width: 100%;
    height: 100%;
    display: flex;
    align-items: center;
    justify-content: center;
    background-size: 300% 300%;
    background-image: linear-gradient(-45deg, #004d4d 10%, #000 50%, #000 50%, #004d4d 90%);
    -webkit-animation: AnimateBG 30s ease infinite;
    animation: AnimateBG 30s ease infinite;
    /* 004d4d */
}

@-webkit-keyframes AnimateBG {
    0% {
        background-position: 0% 50%;
    }

    50% {
        background-position: 100% 50%;
    }

    100% {
        background-position: 0% 50%;
    }
}

@keyframes AnimateBG {
    0% {
        background-position: 0% 50%;
    }

    50% {
        background-position: 100% 50%;
    }

    100% {
        background-position: 0% 50%;
    }
}