body {
  margin: 0;
  background-color: #ede7d6;
  font-family: 'Yu Gothic', 'Meiryo', sans-serif;
  color: #000000;
}

#container {
  display: flex;
  flex-direction: row-reverse;
  height: 100vh;
}

#resizer {
  position: absolute;
  top: 0;
  left: 0;
  width: 5px;
  height: 100%;
  cursor: ew-resize;
  background-color: #ccc;
  z-index: 10;
}

#menu {
  width: 120px;
  min-width: 100px;   /* 最小幅：これ以下にはならない */
  max-width: 200px;   /* 最大幅：これ以上にはならない */


  background-color: #f9f4e6;
  border-left: 2px solid #b5a98f;
  padding: 15px;
  overflow-y: auto;
  box-shadow: -2px 0 5px rgba(0, 0, 0, 0.1);
  position: relative; /* resizerを配置するために必要 */
}

#bookList {
  transition: opacity 0.3s;
}
#selectedBookArea {
  margin-top: 10px;
}


#viewer {
  flex: 1;
  padding: 20px;
  overflow-y: auto;
  height: 100vh;
  box-sizing: border-box;
  background: url('https://www.transparenttextures.com/patterns/book-cover.png');
}

#pageContent {
  display: block; /* または display: flex; など */
}

.button {
  display: block;
  margin: 8px 0;
  padding: 12px;
  font-size: 15px;
  background-color: #e6ddc6;
  border: 1px solid #b5a98f;
  border-radius: 6px;
  color: #3e3625;
  text-align: left;
  cursor: pointer;
  transition: background-color 0.2s;
}

.button:hover {
  background-color: #d6ccb4;
}

.button.active {
  background-color: #b5a98f;
  color: white;
}

.volumes {
  margin-left: 12px;
}

#chapterTitle .button {
  display: inline-block;
  margin: 4px;
}

.paper {
  background-color: #fcf9f3;
  padding: 30px;
  border: 1px solid #d3c6ac;
  border-radius: 8px;
  box-shadow: 0 0 10px rgba(0, 0, 0, 0.05);
  line-height: 1.8;
  font-size: 16px;
  color: #000000;
}

.pageNavigator {
  display: flex;
  justify-content: space-between;
  align-items: center;
  background-color: #f5efdd;
  padding: 20px;
  border-top: 2px solid #b5a98f;
  border-bottom: 2px solid #b5a98f;
  font-size: 18px;
}

.pageNavigator button {
  background-color: #d6ccb4;
  border: 1px solid #b5a98f;
  padding: 12px 20px;
  border-radius: 6px;
  font-size: 16px;
  cursor: pointer;
}