#flipbook {
  margin: 60px auto 0px 320px;
  width: calc(100% - 320px);
  display: flex;
  justify-content: center;
}

@media (max-width: 800px) {
  /* make sure that the sidebar is always on top of the flipbook */
  aside {
    z-index: 99;
  }

  #flipbook {
    margin-left: 0px;
    width: 100%;
  }
}