body {
    margin: 0;
    /* We DON'T set height: 100vh; here as that breaks scrolling on long content*/
    position: relative;
    background-color: #1a1a1a;

}

.background-wrapper {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    overflow: hidden;
    z-index: -1;
}

.bg-band {
    position: absolute;
    width: 125%;
    height: 150px;
    opacity: 0.8;
    background-color: rgba(0, 255, 255, .3);
    animation: slideBand 6s ease-in-out infinite alternate;
}
.bg-band:nth-child(1){
    top: -100px;
    left: -50px;
    transform: rotate(-30deg);
    animation-delay: -3s;

}

.bg-band:nth-child(2){
    top: -100px;
    left: 50px;
    transform: rotate(45deg);
    background-color: rgba(255, 0, 255, 0.4);
    animation-delay: 0s;
}
.bg-band:nth-child(3){
    top: -100px;
    left: -50px;
    transform: rotate(30deg);
    background-color: rgba(0, 0, 255, .5);
    animation-delay: -2s;
}
.bg-band:nth-child(4){
    top: -100px;
    left: 0px;
    transform: rotate(-45deg);
    background-color: rgba(0, 255, 0, 0.4);
    animation-delay: -4s;
}
@keyframes slideBand {
    0% {
        transform:  translateY(0) rotate(0deg);
    }
    100%{
        transform: translateY(150vh)  rotate(0deg);
    }
}