#container{
    position: relative;
    width:100%;
    height:100vh;
    background-image: url(background.jpg);
    background-size: cover;
    background-position: center;
    overflow: hidden;
    display: flex;
    justify-content: center;
    align-items: center;
}

.snow{
    position: absolute;
    top:0;
    left:0;
    width:50px;
    height:50px;
    background-image: url(snow.png);
    background-size: cover;
    animation: animationSnow 4s ease-in-out infinite;
}
@keyframes animationSnow{
    0%{
        transform: translate(0,0);
        opacity: 0;
    }
    50%{
        opacity: 1;
    }
    100%{
        opacity: 0;
        transform: translate(100px,50vh);
    }
}