@keyframes moveBg {
    0% { background-position: center top; }
    50% { background-position: center center; }
    100% { background-position: center bottom; }
}

.movingBg {
    background-size: cover; 
    background-repeat: no-repeat;
    background-position: center;
    animation: moveBg 10s infinite alternate ease-in-out;
}