html, body {
    width: 100vw;
    height: 100vh;
    overflow-x: hidden;
    display: -webkit-box;
    display: -ms-flexbox;
    display: flex;
    -webkit-box-pack: center;
        -ms-flex-pack: center;
            justify-content: center;
    -webkit-box-align: center;
        -ms-flex-align: center;
            align-items: center;
}