body {
    padding:0;
    margin:0;
    overflow:hidden;
	height: 600px;
}
canvas {
    padding:0;
    margin:0;
}
div.btnbg {
    display: flex;
    position: fixed;
    left: 0;
    top: 0;
    width: 100%;
    height: 100%;
    justify-content: center;
}

.center {
      display: flex;
    align-items: center;
    justify-content: center;
}

.center .h1 {
	flex: 1;
}