body {
  margin: 0;
  background: #333;
  padding: env(safe-area-inset-top) env(safe-area-inset-right)
           env(safe-area-inset-bottom) env(safe-area-inset-left);
  display: flex;
  justify-content: center;
  align-items: center;
  height: 100vh;
}

#book {
  /* width: 800px;
  height: 600px; bsp */
  width: 500px;
  height: 350px;
}

.page img {
  width: 100%;
  height: 100%;
  object-fit: contain;
  display: block;
}