body {
    margin: 0;
    background: #000;
    color: white;
    overflow: hidden;
}
.center0 {
    display: flex;
    justify-content: center;
    align-items: center;
    height: 100%;
}
.center {
    width: calc(min(80vh, 80vw));
    height: calc(min(80vh, 80vw));
}
.cvs {
    position: fixed;
    top: 0px;
    left: 0px;
    width: 100%;
    height: 100%;
}