bg.css

/* Thanks WebStylePress on YouTube for this bg effect! */

.circles {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    overflow: hidden;
}

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

.circles div {
    position: absolute;
    display: block;
    width: 20px;
    height: 20px;
    background: #ffffff11;
    bottom: -150px;
    animation: animate 25s ease-in infinite;
}

.circles div:nth-child(1) {
    left: 25%;
    width: 80px;
    height: 80px;
    animation-delay: 0s;
}

.circles div:nth-child(2) {
    left: 10%;
    width: 20px;
    height: 20px;
    animation-delay: 2s;
    animation-duration: 12s;
}

.circles div:nth-child(3) {
    left: 70%;
    width: 20px;
    height: 20px;
    animation-delay: 4s;
}

.circles div:nth-child(4) {
    left: 40%;
    width: 60px;
    height: 60px;
    animation-delay: 0s;
    animation-duration: 18s;
}

.circles div:nth-child(5) {
    left: 65%;
    width: 20px;
    height: 20px;
    animation-delay: 0s;
}

.circles div:nth-child(6) {
    left: 75%;
    width: 110px;
    height: 110px;
    animation-delay: 3s;
}

.circles div:nth-child(7) {
    left: 35%;
    width: 150px;
    height: 150px;
    animation-delay: 7s;
}

.circles div:nth-child(8) {
    left: 50%;
    width: 25px;
    height: 25px;
    animation-delay: 15s;
    animation-duration: 45s;
}

.circles div:nth-child(9) {
    left: 20%;
    width: 15px;
    height: 15px;
    animation-delay: 2s;
    animation-duration: 35s;
}

.circles div:nth-child(10) {
    left: 85%;
    width: 150px;
    height: 150px;
    animation-delay: 0s;
    animation-duration: 11s;
}