@keyframes animate {
    0%{
        transform: translateY(0) rotate(0deg);
        opacity: 1;
        border-radius: 0;
    }
    100%{
        transform: translateY(-1000px) rotate(720deg);
        opacity: 0;
        border-radius: 50%;
    }
}

.background {
    position: fixed;
    width: 100%;
    height: 100vh;
    top: 0;
    left: 0;
    margin: 0;
    padding: 0;
    background:var(--background);
    overflow: hidden;
    z-index: -1000;
}
.backgroundItem {
    position: absolute;
    display: block;
    list-style: none;
    width: 20px;
    height: 20px;
    background: var(--background-item);
    animation: animate 25s linear infinite;
}

.backgroundItem:nth-child(0) {
    left: 13%;
    width: 112px;
    height: 112px;
    bottom: -112px;
    animation-delay: 1s;
}
.backgroundItem:nth-child(1) {
    left: 16%;
    width: 139px;
    height: 139px;
    bottom: -139px;
    animation-delay: 1s;
}
.backgroundItem:nth-child(2) {
    left: 7%;
    width: 225px;
    height: 225px;
    bottom: -225px;
    animation-delay: 10s;
}
.backgroundItem:nth-child(3) {
    left: 79%;
    width: 203px;
    height: 203px;
    bottom: -203px;
    animation-delay: 5s;
}
.backgroundItem:nth-child(4) {
    left: 36%;
    width: 158px;
    height: 158px;
    bottom: -158px;
    animation-delay: 8s;
}
.backgroundItem:nth-child(5) {
    left: 61%;
    width: 91px;
    height: 91px;
    bottom: -91px;
    animation-delay: 9s;
}
.backgroundItem:nth-child(6) {
    left: 5%;
    width: 203px;
    height: 203px;
    bottom: -203px;
    animation-delay: 9s;
}
.backgroundItem:nth-child(7) {
    left: 29%;
    width: 232px;
    height: 232px;
    bottom: -232px;
    animation-delay: 22s;
}
.backgroundItem:nth-child(8) {
    left: 56%;
    width: 211px;
    height: 211px;
    bottom: -211px;
    animation-delay: 16s;
}
.backgroundItem:nth-child(9) {
    left: 49%;
    width: 151px;
    height: 151px;
    bottom: -151px;
    animation-delay: 44s;
}
.backgroundItem:nth-child(10) {
    left: 88%;
    width: 126px;
    height: 126px;
    bottom: -126px;
    animation-delay: 33s;
}
.backgroundItem:nth-child(11) {
    left: 1%;
    width: 105px;
    height: 105px;
    bottom: -105px;
    animation-delay: 39s;
}