.snow {
    position: fixed;
    width: 20px;
    height: 20px;
    background: white;
    border-radius: 50%;
    z-index: 9999999;
    animation: snowfall 10s linear infinite;
    box-shadow: 0 0 10px white;
}

@keyframes snowfall {
    0% {
        transform: translateY(-20px);
    }
    100% {
        transform: translateY(100vh);
    }
}