span {
    position: absolute;
    z-index: 0;
    bottom: 0;
    border-radius: 50%;
    /* 径向渐变 */
    background: radial-gradient(circle at 72% 28%, #fff 3px, #a8e8ff 8%, #dfedf2, #aad7f9 100%);
    /* 泡泡内阴影 */
    box-shadow: inset 0 0 6px #fff,
        inset 3px 0 6px #dcf6ff,
        inset 2px -2px 10px #adeaff,
        inset 0 0 60px #edf1f1,
        0 0 20px #fff;
    /* 动画 */
    animation: myMove 10s linear infinite;
}

@keyframes myMove {
    0% {
        transform: translateY(0%);
        opacity: 1;
    }

    50% {
        transform: translate(15%, -1000%) scale(1.25);
    }

    75% {
        transform: translate(-25%, -2000%) scale(1.5);
		opacity: .9
    }

    99% {
        opacity: .8;
    }

    100% {
        transform: translateY(-3000%) scale(1.75);
        opacity: 0;
    }
}