html, body {
    margin: 0;
    padding: 0;
    width: 100%;
    height: 100%;
    background: #000;
    overflow: hidden;
}
.wrap {
    width: 100vw;
    height: 100vh;
    display: flex;
    align-items: center;
    justify-content: center;
}
h1 {
    margin: 0;
    color: #fff;
    font-family: Arial, Helvetica, sans-serif;
    font-weight: bold;
    /* sized relative to viewport so it stays big on a small 640x480 screen */
    font-size: 18vw;
    line-height: 1;
    text-align: center;
    user-select: none;
}