/* 全局样式 */
:root {
  --primary-color: #4A90A4;
  --secondary-color: #2C3E50;
  --accent-color: #E74C3C;
  --bg-color: #F8F9FA;
  --card-bg: #FFFFFF;
  --text-color: #333333;
  --text-light: #666666;
  --border-color: #E0E0E0;
  --learning-color: #3498DB;
  --fitness-color: #E74C3C;
  --sports-color: #27AE60;
  --shadow: 0 2px 10px rgba(0, 0, 0, 0.1);
}

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

body {
  font-family: 'Segoe UI', 'PingFang SC', 'Microsoft YaHei', sans-serif;
  background-color: var(--bg-color);
  color: var(--text-color);
  line-height: 1.6;
}

a {
  text-decoration: none;
  color: inherit;
}

/* 头部导航 */
.header {
  background: linear-gradient(135deg, var(--primary-color), var(--secondary-color));
  color: white;
  padding: 0;
  position: sticky;
  top: 0;
  z-index: 1000;
  box-shadow: var(--shadow);
}

.nav {
  max-width: 1200px;
  margin: 0 auto;
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 15px 20px;
}

.logo {
  font-size: 1.8rem;
  font-weight: bold;
  letter-spacing: 2px;
}

.nav-links {
  display: flex;
  gap: 30px;
  list-style: none;
}

.nav-links a {
  color: white;
  font-weight: 500;
  transition: opacity 0.3s;
  padding: 8px 16px;
  border-radius: 20px;
}

.nav-links a:hover {
  background: rgba(255, 255, 255, 0.2);
}

.nav-links a.active {
  background: rgba(255, 255, 255, 0.3);
}

.lang-switch {
  background: rgba(255, 255, 255, 0.2);
  border: 1px solid rgba(255, 255, 255, 0.4);
  color: white;
  padding: 8px 16px;
  border-radius: 20px;
  cursor: pointer;
  font-size: 0.9rem;
  transition: all 0.3s;
}

.lang-switch:hover {
  background: rgba(255, 255, 255, 0.3);
}

/* 主要内容区域 */
.main {
  max-width: 1200px;
  margin: 0 auto;
  padding: 30px 20px;
}

/* 页面标题 */
.page-header {
  text-align: center;
  margin-bottom: 40px;
}

.page-header h1 {
  font-size: 2.5rem;
  color: var(--secondary-color);
  margin-bottom: 10px;
}

.page-header p {
  color: var(--text-light);
  font-size: 1.1rem;
}

/* 分类标签 */
.category-tabs {
  display: flex;
  justify-content: center;
  gap: 15px;
  margin-bottom: 30px;
  flex-wrap: wrap;
}

.category-tab {
  padding: 10px 25px;
  border-radius: 25px;
  font-weight: 500;
  cursor: pointer;
  transition: all 0.3s;
  border: 2px solid transparent;
  background: var(--card-bg);
}

.category-tab:hover {
  transform: translateY(-2px);
  box-shadow: var(--shadow);
}

.category-tab.active,
.category-tab[data-category="all"].active {
  background: var(--primary-color);
  color: white;
}

.category-tab[data-category="learning"] {
  border-color: var(--learning-color);
  color: var(--learning-color);
}

.category-tab[data-category="learning"].active {
  background: var(--learning-color);
  color: white;
}

.category-tab[data-category="fitness"] {
  border-color: var(--fitness-color);
  color: var(--fitness-color);
}

.category-tab[data-category="fitness"].active {
  background: var(--fitness-color);
  color: white;
}

.category-tab[data-category="sports"] {
  border-color: var(--sports-color);
  color: var(--sports-color);
}

.category-tab[data-category="sports"].active {
  background: var(--sports-color);
  color: white;
}

.category-tab[data-category="leisure"] {
  border-color: #9B59B6;
  color: #9B59B6;
}

.category-tab[data-category="leisure"].active {
  background: #9B59B6;
  color: white;
}

/* 分类标签（小） */
.category-badge {
  display: inline-block;
  padding: 4px 12px;
  border-radius: 12px;
  font-size: 0.8rem;
  font-weight: 500;
  color: white;
}

.category-badge.learning {
  background: var(--learning-color);
}

.category-badge.fitness {
  background: var(--fitness-color);
}

.category-badge.sports {
  background: var(--sports-color);
}

.category-badge.leisure {
  background: #9B59B6;
}

/* 内容网格 */
.content-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
  gap: 25px;
}

/* 卡片样式 */
.card {
  background: var(--card-bg);
  border-radius: 12px;
  overflow: hidden;
  box-shadow: var(--shadow);
  transition: all 0.3s;
}

.card:hover {
  transform: translateY(-5px);
  box-shadow: 0 5px 20px rgba(0, 0, 0, 0.15);
}

.card-image {
  width: 100%;
  height: 180px;
  object-fit: cover;
  background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
}

.card-image.placeholder {
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 3rem;
  color: white;
}

.card-content {
  padding: 20px;
}

.card-meta {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 10px;
}

.card-date {
  color: var(--text-light);
  font-size: 0.85rem;
}

.card-title {
  font-size: 1.2rem;
  font-weight: 600;
  margin-bottom: 10px;
  line-height: 1.4;
  display: -webkit-box;
  -webkit-line-clamp: 2;
  -webkit-box-orient: vertical;
  overflow: hidden;
}

.card-excerpt {
  color: var(--text-light);
  font-size: 0.95rem;
  display: -webkit-box;
  -webkit-line-clamp: 3;
  -webkit-box-orient: vertical;
  overflow: hidden;
}

/* 视频卡片特殊样式 */
.video-card .card-image {
  position: relative;
}

.video-duration {
  position: absolute;
  bottom: 10px;
  right: 10px;
  background: rgba(0, 0, 0, 0.7);
  color: white;
  padding: 3px 8px;
  border-radius: 4px;
  font-size: 0.8rem;
}

.play-icon {
  position: absolute;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
  width: 60px;
  height: 60px;
  background: rgba(255, 255, 255, 0.9);
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.5rem;
  color: var(--primary-color);
  opacity: 0;
  transition: opacity 0.3s;
}

.video-card:hover .play-icon {
  opacity: 1;
}

/* 文章/视频详情页 */
.detail-container {
  max-width: 900px;
  margin: 0 auto;
}

.detail-header {
  margin-bottom: 30px;
}

.detail-header h1 {
  font-size: 2rem;
  margin-bottom: 15px;
  color: var(--secondary-color);
}

.detail-meta {
  display: flex;
  gap: 20px;
  color: var(--text-light);
  margin-bottom: 20px;
}

.detail-cover {
  width: 100%;
  max-height: 400px;
  object-fit: cover;
  border-radius: 12px;
  margin-bottom: 30px;
}

.detail-content {
  background: var(--card-bg);
  padding: 40px;
  border-radius: 12px;
  box-shadow: var(--shadow);
  line-height: 1.8;
}

.detail-content p {
  margin-bottom: 20px;
}

/* 视频播放器 */
.video-player {
  width: 100%;
  border-radius: 12px;
  margin-bottom: 30px;
  background: black;
}

.video-info {
  background: var(--card-bg);
  padding: 30px;
  border-radius: 12px;
  box-shadow: var(--shadow);
}

/* 空状态 */
.empty-state {
  text-align: center;
  padding: 60px 20px;
  color: var(--text-light);
}

.empty-state svg {
  width: 100px;
  height: 100px;
  margin-bottom: 20px;
  opacity: 0.5;
}

/* 加载状态 */
.loading {
  text-align: center;
  padding: 40px;
  color: var(--text-light);
}

.loading-spinner {
  width: 40px;
  height: 40px;
  border: 3px solid var(--border-color);
  border-top-color: var(--primary-color);
  border-radius: 50%;
  animation: spin 1s linear infinite;
  margin: 0 auto 15px;
}

@keyframes spin {
  to { transform: rotate(360deg); }
}

/* 返回按钮 */
.back-btn {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  color: var(--primary-color);
  margin-bottom: 20px;
  font-weight: 500;
  transition: color 0.3s;
}

.back-btn:hover {
  color: var(--secondary-color);
}

/* 页脚 */
.footer {
  background: var(--secondary-color);
  color: white;
  text-align: center;
  padding: 30px 20px;
  margin-top: 60px;
}

.footer p {
  opacity: 0.8;
}

/* 响应式设计 */
@media (max-width: 768px) {
  .nav {
    flex-direction: column;
    gap: 15px;
  }

  .nav-links {
    gap: 15px;
    flex-wrap: wrap;
    justify-content: center;
  }

  .page-header h1 {
    font-size: 1.8rem;
  }

  .content-grid {
    grid-template-columns: 1fr;
  }

  .detail-content {
    padding: 25px;
  }
}

/* ========== 管理后台样式 ========== */
.admin-body {
  background: #f0f2f5;
}

.admin-container {
  display: flex;
  min-height: 100vh;
}

/* 侧边栏 */
.admin-sidebar {
  width: 250px;
  background: var(--secondary-color);
  color: white;
  padding: 20px 0;
  position: fixed;
  height: 100vh;
  overflow-y: auto;
}

.admin-logo {
  padding: 10px 20px 30px;
  font-size: 1.5rem;
  font-weight: bold;
  border-bottom: 1px solid rgba(255, 255, 255, 0.1);
  margin-bottom: 20px;
}

.admin-menu {
  list-style: none;
}

.admin-menu a {
  display: flex;
  align-items: center;
  gap: 12px;
  padding: 15px 25px;
  color: rgba(255, 255, 255, 0.7);
  transition: all 0.3s;
}

.admin-menu a:hover,
.admin-menu a.active {
  background: rgba(255, 255, 255, 0.1);
  color: white;
  border-left: 3px solid var(--primary-color);
}

.admin-menu-icon {
  font-size: 1.2rem;
}

/* 主内容区 */
.admin-main {
  flex: 1;
  margin-left: 250px;
  padding: 30px;
}

.admin-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 30px;
}

.admin-header h1 {
  font-size: 1.8rem;
  color: var(--secondary-color);
}

.admin-user {
  display: flex;
  align-items: center;
  gap: 15px;
}

.logout-btn {
  background: var(--accent-color);
  color: white;
  border: none;
  padding: 8px 20px;
  border-radius: 5px;
  cursor: pointer;
  transition: background 0.3s;
}

.logout-btn:hover {
  background: #c0392b;
}

/* 统计卡片 */
.stats-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
  gap: 20px;
  margin-bottom: 30px;
}

.stat-card {
  background: white;
  padding: 25px;
  border-radius: 10px;
  box-shadow: var(--shadow);
}

.stat-card h3 {
  color: var(--text-light);
  font-size: 0.9rem;
  margin-bottom: 10px;
}

.stat-card .number {
  font-size: 2.5rem;
  font-weight: bold;
  color: var(--secondary-color);
}

.stat-card.learning .number { color: var(--learning-color); }
.stat-card.fitness .number { color: var(--fitness-color); }
.stat-card.sports .number { color: var(--sports-color); }

/* 表格 */
.admin-table-container {
  background: white;
  border-radius: 10px;
  box-shadow: var(--shadow);
  overflow: hidden;
}

.table-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 20px;
  border-bottom: 1px solid var(--border-color);
}

.table-header h2 {
  font-size: 1.2rem;
  color: var(--secondary-color);
}

.table-actions {
  display: flex;
  align-items: center;
  gap: 15px;
}

.search-input {
  padding: 10px 20px;
  border: 2px solid var(--border-color);
  border-radius: 25px;
  font-size: 0.9rem;
  width: 250px;
  outline: none;
  transition: border-color 0.3s;
}

.search-input:focus {
  border-color: var(--primary-color);
}

.add-btn {
  background: var(--primary-color);
  color: white;
  border: none;
  padding: 10px 20px;
  border-radius: 5px;
  cursor: pointer;
  display: flex;
  align-items: center;
  gap: 8px;
  transition: background 0.3s;
}

.add-btn:hover {
  background: #3d7a8c;
}

.admin-table {
  width: 100%;
  border-collapse: collapse;
}

.admin-table th,
.admin-table td {
  padding: 15px 20px;
  text-align: left;
  border-bottom: 1px solid var(--border-color);
}

.admin-table th {
  background: #f8f9fa;
  font-weight: 600;
  color: var(--text-light);
}

.admin-table tr:hover {
  background: #f8f9fa;
}

.action-btns {
  display: flex;
  gap: 10px;
}

.action-btn {
  padding: 6px 12px;
  border: none;
  border-radius: 4px;
  cursor: pointer;
  font-size: 0.85rem;
  transition: all 0.3s;
}

.action-btn.edit {
  background: #3498db;
  color: white;
}

.action-btn.edit:hover {
  background: #2980b9;
}

.action-btn.delete {
  background: var(--accent-color);
  color: white;
}

.action-btn.delete:hover {
  background: #c0392b;
}

/* 模态框 */
.modal {
  display: none;
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background: rgba(0, 0, 0, 0.5);
  z-index: 2000;
  align-items: center;
  justify-content: center;
}

.modal.active {
  display: flex;
}

.modal-content {
  background: white;
  border-radius: 10px;
  width: 90%;
  max-width: 600px;
  max-height: 90vh;
  overflow-y: auto;
}

.modal-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 20px;
  border-bottom: 1px solid var(--border-color);
}

.modal-header h2 {
  font-size: 1.3rem;
  color: var(--secondary-color);
}

.modal-close {
  background: none;
  border: none;
  font-size: 1.5rem;
  cursor: pointer;
  color: var(--text-light);
}

.modal-body {
  padding: 25px;
}

/* 表单样式 */
.form-group {
  margin-bottom: 20px;
}

.form-group label {
  display: block;
  margin-bottom: 8px;
  font-weight: 500;
  color: var(--secondary-color);
}

.form-group input,
.form-group select,
.form-group textarea {
  width: 100%;
  padding: 12px;
  border: 1px solid var(--border-color);
  border-radius: 6px;
  font-size: 1rem;
  transition: border-color 0.3s;
}

.form-group input:focus,
.form-group select:focus,
.form-group textarea:focus {
  outline: none;
  border-color: var(--primary-color);
}

.form-group textarea {
  min-height: 120px;
  resize: vertical;
}

.form-row {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 15px;
}

.submit-btn {
  width: 100%;
  background: var(--primary-color);
  color: white;
  border: none;
  padding: 14px;
  border-radius: 6px;
  font-size: 1rem;
  font-weight: 500;
  cursor: pointer;
  transition: background 0.3s;
}

.submit-btn:hover {
  background: #3d7a8c;
}

.submit-btn:disabled {
  background: #ccc;
  cursor: not-allowed;
}

/* 登录页面 */
.login-container {
  min-height: 100vh;
  display: flex;
  align-items: center;
  justify-content: center;
  background: linear-gradient(135deg, var(--primary-color), var(--secondary-color));
}

.login-box {
  background: white;
  padding: 50px 40px;
  border-radius: 15px;
  box-shadow: 0 10px 40px rgba(0, 0, 0, 0.2);
  width: 100%;
  max-width: 400px;
}

.login-box h1 {
  text-align: center;
  color: var(--secondary-color);
  margin-bottom: 10px;
}

.login-box p {
  text-align: center;
  color: var(--text-light);
  margin-bottom: 30px;
}

.login-box .form-group {
  margin-bottom: 25px;
}

.login-error {
  background: #fee;
  color: var(--accent-color);
  padding: 10px 15px;
  border-radius: 6px;
  margin-bottom: 20px;
  display: none;
}

.login-error.show {
  display: block;
}

/* 响应式管理后台 */
@media (max-width: 768px) {
  .admin-sidebar {
    width: 60px;
    padding: 15px 0;
  }

  .admin-logo {
    font-size: 0;
    padding: 10px;
    text-align: center;
  }

  .admin-logo::first-letter {
    font-size: 1.5rem;
  }

  .admin-menu a span {
    display: none;
  }

  .admin-menu a {
    justify-content: center;
    padding: 15px;
  }

  .admin-main {
    margin-left: 60px;
    padding: 20px;
  }

  .form-row {
    grid-template-columns: 1fr;
  }
}