body{
    margin: 0;
    padding: 0;
    overflow: hidden;
}
.pattern{
    width: 100%;
    height: 100vh;
    background: url(bg.png);
    background-position: 0 0;
    animation: pattern 15s linear infinite;
}
@keyframes pattern{
    from{
        background-position: 0 0;
    }
    to{
        background-position: 800px 600px;
    }
}