html, body {
  padding: 0;
  margin: 0;
}

.canvasdiv {
    background: url(../img/ghep.png) no-repeat center center;
    background-size: 2000px;
    opacity: .15;
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
}