.snowflake {
    color: #fff;
    font-size: 1.5em;
    font-family: Arial, sans-serif;
    text-shadow: 0 0 5px #000;
    position: fixed;
    top: -10%;
    z-index: 9999;
    user-select: none;
    cursor: default;
    animation: snowflakes-fall 10s linear infinite, snowflakes-shake 3s ease-in-out infinite;
}

@keyframes snowflakes-fall {
    0% {
        top: -10%;
    }

    100% {
        top: 100%;
    }
}

@keyframes snowflakes-shake {

    0%,
    100% {
        transform: translateX(0);
    }

    50% {
        transform: translateX(20px);
    }
}