:root {
  --primary-color: #800000;
  --primary-hover: #a00000;
  --bg-main: #f8f9fa;
  --text-color: #222222;
  --text-muted: #666666;
  --border-color: #dddddd;
  --highlight-box: #edf7ed;
  --highlight-border: #c3e6cb;
  --highlight-text: #155724;
}

body {
  margin: 0;
  padding: 0;
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  background-color: var(--bg-main);
  color: var(--text-color);
  line-height: 1.5;
}

/* Header 继承 ArXiv Sanity 酒红色彩与线条 */
.header-bar {
  background-color: var(--primary-color);
  color: #ffffff;
  padding: 12px 24px;
  display: flex;
  justify-content: space-between;
  align-items: center;
  border-bottom: 2px solid #5a0000;
}

.header-left .title {
  color: #ffffff;
  font-size: 1.3rem;
  font-weight: bold;
  text-decoration: none;
}

.header-left .subtitle {
  font-size: 0.8rem;
  color: #ffcccc;
  margin-top: 2px;
}

.header-right a {
  color: #ffffff;
  text-decoration: none;
  font-size: 0.9rem;
}

/* 页面容器 */
.container {
  max-width: 1140px;
  margin: 20px auto;
  padding: 0 15px;
}

/* 全局搜索与分类筛选 */
.search-filter-bar {
  background: #ffffff;
  border: 1px solid var(--border-color);
  padding: 12px 16px;
  border-radius: 4px;
  margin-bottom: 20px;
  display: flex;
  gap: 12px;
  align-items: center;
}

.search-filter-bar input[type="text"] {
  flex: 1;
  padding: 8px 12px;
  border: 1px solid var(--border-color);
  border-radius: 3px;
  font-size: 0.9rem;
}

.search-filter-bar button {
  background: var(--primary-color);
  color: #fff;
  border: none;
  padding: 8px 16px;
  border-radius: 3px;
  cursor: pointer;
}

.search-filter-bar button:hover {
  background: var(--primary-hover);
}

/* 电子书网格布局 */
.book-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(210px, 1fr));
  gap: 20px;
}

/* 电子书卡片 */
.book-card {
  background: #ffffff;
  border: 1px solid var(--border-color);
  border-radius: 4px;
  padding: 12px;
  display: flex;
  flex-direction: column;
  justify-content: space-between;
  transition: transform 0.15s ease, box-shadow 0.15s ease;
}

.book-card:hover {
  transform: translateY(-2px);
  box-shadow: 0 4px 12px rgba(0, 0, 0, 0.08);
}

.book-cover {
  width: 100%;
  height: 240px;
  object-fit: cover;
  border-radius: 2px;
  border: 1px solid #eee;
  margin-bottom: 10px;
}

.book-card-title {
  font-weight: bold;
  font-size: 1rem;
  color: #111;
  text-decoration: none;
  margin-bottom: 4px;
  display: -webkit-box;
  -webkit-line-clamp: 2;
  -webkit-box-orient: vertical;
  overflow: hidden;
}

.book-card-author {
  font-size: 0.85rem;
  color: var(--text-muted);
  margin-bottom: 8px;
}

.book-badge-box {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-top: auto;
  padding-top: 8px;
  border-top: 1px solid #f0f0f0;
}

.category-tag {
  background: #f0f0f0;
  color: #444;
  font-size: 0.75rem;
  padding: 2px 6px;
  border-radius: 2px;
}

.price-text {
  font-weight: bold;
  color: var(--primary-color);
  font-size: 0.9rem;
}

/* 表单与通用卡片 */
.paper-card, .form-box {
  background: #ffffff;
  border: 1px solid var(--border-color);
  border-radius: 4px;
  padding: 20px;
  margin-bottom: 20px;
}

.paper-green-box {
  background-color: var(--highlight-box);
  border: 1px solid var(--highlight-border);
  color: var(--highlight-text);
  padding: 12px 15px;
  border-radius: 3px;
  font-size: 0.9rem;
  line-height: 1.6;
}

/* 按钮样式 */
.btn-submit {
  background-color: var(--primary-color);
  color: #ffffff;
  border: none;
  padding: 8px 16px;
  border-radius: 3px;
  cursor: pointer;
  font-weight: bold;
}

.btn-submit:hover {
  background-color: var(--primary-hover);
}

.btn-logout {
  padding: 4px 8px;
  font-size: 0.8rem;
  background: transparent;
  border: 1px solid #ffffff;
  color: #ffffff;
  border-radius: 3px;
  text-decoration: none;
}

.form-group {
  margin-bottom: 15px;
}

.form-group label {
  display: block;
  font-weight: bold;
  margin-bottom: 5px;
  font-size: 0.9rem;
}

.form-control {
  width: 100%;
  padding: 8px 10px;
  box-sizing: border-box;
  border: 1px solid var(--border-color);
  border-radius: 3px;
}

.alert {
  padding: 10px 15px;
  background: #fff3cd;
  border: 1px solid #ffeeba;
  color: #856404;
  border-radius: 3px;
  margin-bottom: 15px;
}

/* 表格全局样式 */
.data-table {
  width: 100%;
  border-collapse: collapse;
  margin-top: 10px;
}

.data-table th, .data-table td {
  border: 1px solid var(--border-color);
  padding: 10px 12px;
  text-align: left;
  font-size: 0.88rem;
}

.data-table th {
  background: #f1f1f1;
}

/* 选项卡 Tab */
.admin-tabs {
  display: flex;
  border-bottom: 2px solid var(--primary-color);
  margin-bottom: 20px;
}

.admin-tab-btn {
  padding: 10px 20px;
  text-decoration: none;
  color: var(--text-color);
  font-weight: bold;
  border: 1px solid transparent;
}

.admin-tab-btn.active {
  background: var(--primary-color);
  color: #ffffff;
  border-radius: 4px 4px 0 0;
}