.page {
    width: 100%;
    height: 100%;
    position: absolute;
    top: 0%;
    left: 0%;
    background-image: url("https://panmacmillan.azureedge.net/pmk11/panmacmillan/files/media/panmacmillan/blogs-2018/autumn-poems-header-min.jpg");
    background-color: #000000;
    background-repeat: no-repeat;
    background-size: cover;
}

.anim span {
    display: inline-block;
    height: 75px;
    width: 75px;
    margin: -280px 40px 54px -34px;
    background: url("http://premiumcoding.com/CSSTricks/fallingLeaves/leaf.png");
    animation: anim 10s infinite linear;
}

    .anim span:nth-child(7h) {
        animation-delay: 2.5s;
    }

    .anim span:nth-child(7n-1) {
        animation-delay: 1.0s;
    }

    .anim span:nth-child(7n-2) {
        animation-delay: 3.5s;
    }

    .anim span:nth-child(7n-3) {
        animation-delay: 5.0s;
    }

    .anim span:nth-child(7n-4) {
        animation-delay: 1.5s;
    }

    .anim span:nth-child(7n-5) {
        animation-delay: 7.0s;
    }

    .anim span:nth-child(7n-6) {
        animation-delay: 9.5s;
    }

@keyframes anim {
    0% {
        width: 75px;
        height: 75px;
        opacity: 1;
        transform: translate(0, 0px) rotateZ(0deg);
    }

    75% {
        width: 75px;
        height: 75px;
        opacity: 1;
        transform: translate(100px, 900px) rotateZ(270deg);
    }

    100% {
        width: 75px;
        height: 75px;
        opacity: 0;
        transform: translate(150px, 900px) rotateZ(360deg);
    }
}