* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

body {
  font-family: serif;
  background: #f6f1e7;
}

#topbar {
  position: fixed;
  top: 0;
  width: 100%;
  height: 50px;
  background: #fff;
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0 16px;
  box-shadow: 0 1px 4px rgba(0,0,0,0.1);
  z-index: 100;
}

#viewer {
  height: calc(100vh - 50px);
  margin-top: 50px;
}

.book {
  border: 1px solid #ccc;
  padding: 10px;
  margin: 10px;
  cursor: pointer;
  border-radius: 4px;
  background: #fff;
}

.book:hover {
  box-shadow: 0 2px 8px rgba(0,0,0,0.15);
}

/* 3Dページめくり風 */
.epub-container {
  transform-style: preserve-3d;
  transition: transform 0.6s;
}