bubbles.css

.bubbles {
    position: absolute;
    width: 100vw;
    height: 100%;
    overflow: hidden;
    top: 0;
    left: 0;
    z-index: -1;
}

.bubble-l {
    position: absolute;
    bottom: -100px;
    width: 40px;
    height: 40px;
    background-color: #f1f1f1;
    border-radius: 50%;
    opacity: 0.5;
    animation: float-left 10s infinite ease-in;
}

.bubble-r {
    position: absolute;
    bottom: -100px;
    width: 40px;
    height: 40px;
    background-color: #f1f1f1;
    border-radius: 50%;
    opacity: 0.5;
    animation: float-right 10s infinite ease-in;
}

.bubble-l:nth-child(1) {
    width: 40px;
    height: 40px;
    left: 10%;
    animation-duration: 8s;
}

.bubble-l:nth-child(2) {
    width: 20px;
    height: 20px;
    left: 20%;
    animation-duration: 5s;
    animation-delay: 1s;
}

.bubble-l:nth-child(3) {
    width: 50px;
    height: 50px;
    left: 35%;
    animation-duration: 7s;
    animation-delay: 2s;
}

.bubble-l:nth-child(4) {
    width: 80px;
    height: 80px;
    left: 50%;
    animation-duration: 11s;
    animation-delay: 0s;
}

.bubble-l:nth-child(5) {
    width: 35px;
    height: 35px;
    left: 55%;
    animation-duration: 6s;
    animation-delay: 1s;
}


.bubble-r:nth-child(6) {
    width: 45px;
    height: 45px;
    left: 65%;
    animation-duration: 8s;
    animation-delay: 3s;
}

.bubble-r:nth-child(7) {
    width: 90px;
    height: 90px;
    left: 70%;
    animation-duration: 12s;
    animation-delay: 2s;
}

.bubble-r:nth-child(8) {
    width: 25px;
    height: 25px;
    left: 80%;
    animation-duration: 6s;
    animation-delay: 2s;
}

.bubble-r:nth-child(9) {
    width: 15px;
    height: 15px;
    left: 70%;
    animation-duration: 5s;
    animation-delay: 1s;
}

.bubble-r:nth-child(10) {
    width: 90px;
    height: 90px;
    left: 25%;
    animation-duration: 10s;
    animation-delay: 4s;
}

@keyframes float-left {
    0% {
        bottom: -100px;
        transform: translateX(0);
    }
    50% {
        transform: translate(100px);
    }
    100% {
        bottom: 1080px;
        transform: translateX(-100px);
    }
}

@keyframes float-right {
    0% {
        bottom: -100px;
        transform: translateX(0);
    }
    50% {
        transform: translate(100px);
    }
    100% {
        bottom: 1080px;
        transform: translateX(200px);
    }
}