html, body, .center-of-screen {
    left: 0;
    right: 0;
    top: 0;
    bottom: 0;
}
body {
    padding: 0;
}
html.fullscreen, html.fullscreen body {
    margin: 0;
    height: 100%;
    width: 100%;
}
.center-of-screen {
    position: fixed;
    display: -webkit-flex;
    display: flex;
    -webkit-align-items: center;
    align-items: center;
    -webkit-justify-content: center;
    justify-content: center;
}
.game-div canvas{
    width: 100vw;
    height: 100vh;
}