html, body {
  margin: 0;
  padding: 0;
  width: 100%;
  height: 100%;
  overflow: hidden;     /* prevent scrollbars on body */
}

#app {
  width: 100%;
  height: 100%;
  overflow: hidden;     /* ensure the canvas container doesn’t allow scroll */
  position: relative;   /* if not already */
}

canvas {
  display: block;
  width: 100%;
  height: 100%;
}