/* 网球 - 教程风格样式 */
/* 主色调: #20c997 青绿色 */

/* CSS 变量 */
:root {
  --accent-color: #20c997;
  --accent-dark: #1ba87e;
  --accent-light: #e6f9f3;
  --text-primary: #2c3e50;
  --text-secondary: #5a6c7d;
  --text-muted: #8b9aa8;
  --bg-primary: #ffffff;
  --bg-secondary: #f8f9fa;
  --bg-tertiary: #eef1f4;
  --border-color: #e1e8ed;
  --shadow-sm: 0 2px 4px rgba(0,0,0,0.05);
  --shadow-md: 0 4px 12px rgba(0,0,0,0.08);
  --shadow-lg: 0 8px 24px rgba(0,0,0,0.12);
  --radius-sm: 6px;
  --radius-md: 10px;
  --radius-lg: 16px;
  --max-width: 1200px;
  --header-height: 64px;
}

/* 重置样式 */
*, *::before, *::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

html {
  scroll-behavior: smooth;
}

body {
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
  font-size: 16px;
  line-height: 1.6;
  color: var(--text-primary);
  background-color: var(--bg-primary);
}

a {
  text-decoration: none;
  color: var(--accent-color);
  transition: color 0.2s ease;
}

a:hover {
  color: var(--accent-dark);
}

img {
  max-width: 100%;
  height: auto;
  display: block;
}

ul, ol {
  list-style: none;
}

/* 容器 */
.container {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 20px;
}

/* Header */
.header {
  position: sticky;
  top: 0;
  z-index: 100;
  background: var(--bg-primary);
  border-bottom: 1px solid var(--border-color);
  height: var(--header-height);
}

.header .container {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 100%;
}

.logo {
  display: flex;
  align-items: center;
  gap: 10px;
  font-size: 1.5rem;
  font-weight: 700;
  color: var(--text-primary);
}

.logo-icon {
  width: 36px;
  height: 36px;
  background: linear-gradient(135deg, var(--accent-color), var(--accent-dark));
  border-radius: var(--radius-sm);
  display: flex;
  align-items: center;
  justify-content: center;
  color: white;
  font-size: 1.2rem;
}

.nav {
  display: flex;
  gap: 32px;
}

.nav a {
  color: var(--text-secondary);
  font-weight: 500;
  font-size: 0.95rem;
}

.nav a:hover,
.nav a.active {
  color: var(--accent-color);
}

.search-box {
  position: relative;
}

.search-box input {
  width: 240px;
  padding: 10px 16px 10px 40px;
  border: 1px solid var(--border-color);
  border-radius: 24px;
  font-size: 0.9rem;
  background: var(--bg-secondary);
  transition: all 0.2s ease;
}

.search-box input:focus {
  outline: none;
  border-color: var(--accent-color);
  background: var(--bg-primary);
}

.search-box::before {
  content: "🔍";
  position: absolute;
  left: 14px;
  top: 50%;
  transform: translateY(-50%);
  font-size: 0.9rem;
  opacity: 0.5;
}

/* 移动端菜单按钮 */
.menu-toggle {
  display: none;
  background: none;
  border: none;
  font-size: 1.5rem;
  cursor: pointer;
  color: var(--text-primary);
}

/* Hero Section */
.hero {
  background: linear-gradient(135deg, var(--accent-light) 0%, var(--bg-primary) 100%);
  padding: 80px 0 60px;
  text-align: center;
}

.hero-title {
  font-size: 2.8rem;
  font-weight: 800;
  color: var(--text-primary);
  margin-bottom: 16px;
  line-height: 1.2;
}

.hero-title span {
  color: var(--accent-color);
}

.hero-desc {
  font-size: 1.15rem;
  color: var(--text-secondary);
  max-width: 600px;
  margin: 0 auto 32px;
}

.hero-cta {
  display: inline-flex;
  gap: 16px;
}

.btn {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 14px 28px;
  border-radius: 28px;
  font-weight: 600;
  font-size: 1rem;
  transition: all 0.2s ease;
  border: none;
  cursor: pointer;
}

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

.btn-primary:hover {
  background: var(--accent-dark);
  color: white;
  transform: translateY(-2px);
  box-shadow: var(--shadow-md);
}

.btn-secondary {
  background: white;
  color: var(--text-primary);
  border: 1px solid var(--border-color);
}

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

/* Stats Section */
.stats-section {
  padding: 40px 0;
  background: var(--bg-primary);
}

.stats-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 24px;
  max-width: 800px;
  margin: 0 auto;
}

.stat-card {
  text-align: center;
  padding: 24px;
  background: var(--bg-secondary);
  border-radius: var(--radius-md);
  border: 1px solid var(--border-color);
}

.stat-number {
  font-size: 2.2rem;
  font-weight: 800;
  color: var(--accent-color);
  line-height: 1;
}

.stat-label {
  font-size: 0.9rem;
  color: var(--text-secondary);
  margin-top: 8px;
}

/* Section Title */
.section-title {
  font-size: 1.5rem;
  font-weight: 700;
  color: var(--text-primary);
  margin-bottom: 24px;
  display: flex;
  align-items: center;
  gap: 10px;
}

.section-title::before {
  content: "";
  width: 4px;
  height: 24px;
  background: var(--accent-color);
  border-radius: 2px;
}

/* Progress Section */
.progress-section {
  padding: 60px 0;
  background: var(--bg-secondary);
}

.current-course {
  background: var(--bg-primary);
  border-radius: var(--radius-lg);
  padding: 32px;
  box-shadow: var(--shadow-sm);
  border: 1px solid var(--border-color);
}

.course-header {
  display: flex;
  gap: 24px;
  margin-bottom: 24px;
}

.course-cover {
  width: 160px;
  height: 100px;
  background: linear-gradient(135deg, var(--accent-color), var(--accent-dark));
  border-radius: var(--radius-md);
  display: flex;
  align-items: center;
  justify-content: center;
  color: white;
  font-size: 3rem;
  flex-shrink: 0;
}

.course-info h3 {
  font-size: 1.3rem;
  font-weight: 700;
  margin-bottom: 8px;
}

.course-meta {
  color: var(--text-muted);
  font-size: 0.9rem;
  margin-bottom: 16px;
}

.progress-bar {
  height: 8px;
  background: var(--bg-tertiary);
  border-radius: 4px;
  overflow: hidden;
  margin-bottom: 8px;
}

.progress-fill {
  height: 100%;
  background: linear-gradient(90deg, var(--accent-color), var(--accent-dark));
  border-radius: 4px;
  transition: width 0.3s ease;
}

.progress-text {
  font-size: 0.85rem;
  color: var(--text-secondary);
  font-weight: 500;
}

/* Course Grid */
.course-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
  gap: 24px;
}

.course-card {
  background: var(--bg-primary);
  border-radius: var(--radius-md);
  overflow: hidden;
  border: 1px solid var(--border-color);
  transition: all 0.2s ease;
}

.course-card:hover {
  transform: translateY(-4px);
  box-shadow: var(--shadow-md);
}

.course-thumb {
  height: 160px;
  background: linear-gradient(135deg, var(--accent-light), var(--bg-secondary));
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 3rem;
}

.course-body {
  padding: 20px;
}

.course-tag {
  display: inline-block;
  padding: 4px 10px;
  background: var(--accent-light);
  color: var(--accent-dark);
  font-size: 0.75rem;
  font-weight: 600;
  border-radius: 12px;
  margin-bottom: 10px;
}

.course-title {
  font-size: 1.05rem;
  font-weight: 600;
  margin-bottom: 8px;
  color: var(--text-primary);
}

.course-desc {
  font-size: 0.9rem;
  color: var(--text-secondary);
  line-height: 1.5;
}

/* Article Lists */
.article-section {
  padding: 60px 0;
}

.article-section.alt {
  background: var(--bg-secondary);
}

.article-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 32px;
}

.article-list {
  background: var(--bg-primary);
  border-radius: var(--radius-md);
  padding: 24px;
  border: 1px solid var(--border-color);
}

.article-list h4 {
  font-size: 1rem;
  font-weight: 600;
  color: var(--text-primary);
  margin-bottom: 16px;
  padding-bottom: 12px;
  border-bottom: 1px solid var(--border-color);
}

.article-list ul li {
  padding: 12px 0;
  border-bottom: 1px solid var(--bg-tertiary);
}

.article-list ul li:last-child {
  border-bottom: none;
}

.article-list a {
  color: var(--text-primary);
  font-size: 0.95rem;
  display: flex;
  align-items: center;
  gap: 8px;
}

.article-list a::before {
  content: "•";
  color: var(--accent-color);
  font-weight: bold;
}

.article-list a:hover {
  color: var(--accent-color);
}

/* Footer */
.footer {
  background: var(--text-primary);
  color: white;
  padding: 48px 0 24px;
}

.footer-grid {
  display: grid;
  grid-template-columns: 2fr 1fr 1fr 1fr;
  gap: 40px;
  margin-bottom: 40px;
}

.footer-brand p {
  color: rgba(255,255,255,0.7);
  margin-top: 16px;
  font-size: 0.95rem;
}

.footer-links h5 {
  font-size: 1rem;
  font-weight: 600;
  margin-bottom: 16px;
}

.footer-links ul li {
  margin-bottom: 10px;
}

.footer-links a {
  color: rgba(255,255,255,0.7);
  font-size: 0.9rem;
}

.footer-links a:hover {
  color: var(--accent-color);
}

.footer-bottom {
  border-top: 1px solid rgba(255,255,255,0.1);
  padding-top: 24px;
  text-align: center;
  color: rgba(255,255,255,0.5);
  font-size: 0.9rem;
}

/* Breadcrumb */
.breadcrumb {
  padding: 20px 0;
  background: var(--bg-secondary);
  border-bottom: 1px solid var(--border-color);
}

.breadcrumb ol {
  display: flex;
  align-items: center;
  gap: 8px;
}

.breadcrumb li {
  font-size: 0.9rem;
  color: var(--text-muted);
}

.breadcrumb li:not(:last-child)::after {
  content: ">";
  margin-left: 8px;
  color: var(--text-muted);
}

.breadcrumb a {
  color: var(--text-secondary);
}

.breadcrumb a:hover {
  color: var(--accent-color);
}

/* Category Header */
.category-header {
  padding: 48px 0 32px;
  background: var(--bg-secondary);
}

.category-title {
  font-size: 2rem;
  font-weight: 700;
  margin-bottom: 12px;
}

.category-desc {
  color: var(--text-secondary);
  margin-bottom: 24px;
}

.category-stats {
  display: flex;
  gap: 24px;
}

.category-stats span {
  font-size: 0.9rem;
  color: var(--text-muted);
}

.category-stats strong {
  color: var(--accent-color);
  font-weight: 600;
}

/* Filter Tabs */
.filter-tabs {
  display: flex;
  gap: 8px;
  margin-bottom: 32px;
  flex-wrap: wrap;
}

.filter-tab {
  padding: 10px 20px;
  border-radius: 20px;
  font-size: 0.9rem;
  font-weight: 500;
  color: var(--text-secondary);
  background: var(--bg-secondary);
  border: 1px solid var(--border-color);
  cursor: pointer;
  transition: all 0.2s ease;
}

.filter-tab:hover,
.filter-tab.active {
  background: var(--accent-color);
  color: white;
  border-color: var(--accent-color);
}

/* Content List */
.content-list {
  padding: 40px 0 60px;
}

.content-item {
  display: flex;
  gap: 24px;
  padding: 24px;
  background: var(--bg-primary);
  border-radius: var(--radius-md);
  border: 1px solid var(--border-color);
  margin-bottom: 16px;
  transition: all 0.2s ease;
}

.content-item:hover {
  box-shadow: var(--shadow-md);
  border-color: var(--accent-color);
}

.content-thumb {
  width: 200px;
  height: 120px;
  background: linear-gradient(135deg, var(--accent-light), var(--bg-secondary));
  border-radius: var(--radius-sm);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 2.5rem;
  flex-shrink: 0;
}

.content-body {
  flex: 1;
}

.content-tag {
  display: inline-block;
  padding: 4px 10px;
  background: var(--accent-light);
  color: var(--accent-dark);
  font-size: 0.75rem;
  font-weight: 600;
  border-radius: 12px;
  margin-bottom: 10px;
}

.content-title {
  font-size: 1.15rem;
  font-weight: 600;
  margin-bottom: 8px;
  color: var(--text-primary);
}

.content-desc {
  font-size: 0.95rem;
  color: var(--text-secondary);
  line-height: 1.5;
  margin-bottom: 12px;
}

.content-meta {
  display: flex;
  gap: 16px;
  font-size: 0.85rem;
  color: var(--text-muted);
}

.content-progress {
  margin-top: 12px;
}

.content-progress .progress-bar {
  max-width: 200px;
}

/* Article Page */
.article-container {
  max-width: 800px;
  margin: 0 auto;
  padding: 40px 20px 60px;
}

.article-header {
  margin-bottom: 32px;
}

.article-title {
  font-size: 2rem;
  font-weight: 700;
  line-height: 1.3;
  margin-bottom: 16px;
}

.article-meta {
  display: flex;
  gap: 20px;
  color: var(--text-muted);
  font-size: 0.9rem;
}

.article-cover {
  width: 100%;
  height: 300px;
  background: linear-gradient(135deg, var(--accent-color), var(--accent-dark));
  border-radius: var(--radius-md);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 5rem;
  color: white;
  margin-bottom: 32px;
}

.article-content {
  font-size: 1.05rem;
  line-height: 1.8;
  color: var(--text-primary);
}

.article-content h2 {
  font-size: 1.5rem;
  font-weight: 700;
  margin: 40px 0 20px;
  color: var(--text-primary);
}

.article-content h3 {
  font-size: 1.25rem;
  font-weight: 600;
  margin: 32px 0 16px;
  color: var(--text-primary);
}

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

.article-content ul,
.article-content ol {
  margin-bottom: 20px;
  padding-left: 24px;
}

.article-content ul li {
  list-style: disc;
  margin-bottom: 8px;
}

.article-content ol li {
  list-style: decimal;
  margin-bottom: 8px;
}

.article-content strong {
  color: var(--accent-dark);
}

/* Notes Section */
.notes-section {
  background: var(--bg-secondary);
  padding: 24px;
  border-radius: var(--radius-md);
  margin: 32px 0;
}

.notes-section h4 {
  font-size: 1.1rem;
  font-weight: 600;
  margin-bottom: 16px;
  display: flex;
  align-items: center;
  gap: 8px;
}

.note-item {
  padding: 16px;
  background: var(--bg-primary);
  border-radius: var(--radius-sm);
  border-left: 3px solid var(--accent-color);
  margin-bottom: 12px;
}

.note-item:last-child {
  margin-bottom: 0;
}

/* Related Section */
.related-section {
  margin-top: 48px;
  padding-top: 32px;
  border-top: 1px solid var(--border-color);
}

.related-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 20px;
  margin-top: 20px;
}

.related-card {
  background: var(--bg-secondary);
  border-radius: var(--radius-md);
  padding: 20px;
  text-align: center;
  transition: all 0.2s ease;
}

.related-card:hover {
  background: var(--accent-light);
}

.related-icon {
  font-size: 2.5rem;
  margin-bottom: 12px;
}

.related-title {
  font-size: 0.95rem;
  font-weight: 600;
  color: var(--text-primary);
}

/* 404 Page */
.error-page {
  min-height: calc(100vh - var(--header-height) - 300px);
  display: flex;
  align-items: center;
  justify-content: center;
  text-align: center;
  padding: 60px 20px;
}

.error-content {
  max-width: 500px;
}

.error-code {
  font-size: 8rem;
  font-weight: 800;
  color: var(--accent-color);
  line-height: 1;
  margin-bottom: 16px;
  opacity: 0.8;
}

.error-title {
  font-size: 1.8rem;
  font-weight: 700;
  margin-bottom: 12px;
}

.error-desc {
  color: var(--text-secondary);
  margin-bottom: 32px;
}

/* Responsive */
@media (max-width: 992px) {
  .hero-title {
    font-size: 2.2rem;
  }

  .article-grid {
    grid-template-columns: repeat(2, 1fr);
  }

  .footer-grid {
    grid-template-columns: repeat(2, 1fr);
  }

  .related-grid {
    grid-template-columns: repeat(2, 1fr);
  }
}

@media (max-width: 768px) {
  .nav {
    display: none;
  }

  .search-box {
    display: none;
  }

  .menu-toggle {
    display: block;
  }

  .hero {
    padding: 60px 0 40px;
  }

  .hero-title {
    font-size: 1.8rem;
  }

  .hero-desc {
    font-size: 1rem;
  }

  .hero-cta {
    flex-direction: column;
    width: 100%;
    padding: 0 20px;
  }

  .btn {
    width: 100%;
    justify-content: center;
  }

  .stats-grid {
    grid-template-columns: 1fr;
    gap: 16px;
  }

  .course-header {
    flex-direction: column;
  }

  .course-cover {
    width: 100%;
    height: 140px;
  }

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

  .content-item {
    flex-direction: column;
  }

  .content-thumb {
    width: 100%;
    height: 160px;
  }

  .footer-grid {
    grid-template-columns: 1fr;
    gap: 32px;
  }

  .article-title {
    font-size: 1.5rem;
  }

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

  .error-code {
    font-size: 5rem;
  }
}

@media (max-width: 480px) {
  .filter-tabs {
    justify-content: center;
  }

  .filter-tab {
    padding: 8px 16px;
    font-size: 0.85rem;
  }
}