/* 学习策略中心 - 全局样式 */
:root {
  --accent-color: #20c997;
  --accent-dark: #1ba87e;
  --text-primary: #2d3748;
  --text-secondary: #718096;
  --text-muted: #a0aec0;
  --bg-primary: #ffffff;
  --bg-secondary: #f7fafc;
  --bg-tertiary: #edf2f7;
  --border-color: #e2e8f0;
  --shadow-sm: 0 1px 3px rgba(0,0,0,0.1);
  --shadow-md: 0 4px 6px rgba(0,0,0,0.1);
  --shadow-lg: 0 10px 15px rgba(0,0,0,0.1);
  --radius-sm: 4px;
  --radius-md: 8px;
  --radius-lg: 12px;
  --max-width: 1200px;
  --header-height: 64px;
}

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

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: var(--bg-primary);
}

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

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

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

.header-inner {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 24px;
  height: 100%;
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.logo {
  font-size: 20px;
  font-weight: 700;
  color: var(--text-primary);
  display: flex;
  align-items: center;
  gap: 8px;
}

.logo-icon {
  width: 32px;
  height: 32px;
  background: var(--accent-color);
  border-radius: var(--radius-md);
  display: flex;
  align-items: center;
  justify-content: center;
  color: white;
  font-size: 16px;
}

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

.nav a {
  color: var(--text-secondary);
  font-weight: 500;
  font-size: 15px;
}

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

.search-box {
  position: relative;
}

.search-box input {
  width: 240px;
  padding: 8px 16px 8px 40px;
  border: 1px solid var(--border-color);
  border-radius: 20px;
  font-size: 14px;
  background: var(--bg-secondary);
  transition: all 0.2s;
}

.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: 14px;
}

/* 面包屑 */
.breadcrumb {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 16px 24px;
  font-size: 14px;
  color: var(--text-secondary);
}

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

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

.breadcrumb span {
  margin: 0 8px;
  color: var(--text-muted);
}

/* Hero 区域 */
.hero {
  background: linear-gradient(135deg, var(--bg-secondary) 0%, var(--bg-tertiary) 100%);
  padding: 60px 24px;
  text-align: center;
}

.hero-inner {
  max-width: var(--max-width);
  margin: 0 auto;
}

.hero h1 {
  font-size: 40px;
  font-weight: 700;
  margin-bottom: 16px;
  color: var(--text-primary);
}

.hero p {
  font-size: 18px;
  color: var(--text-secondary);
  max-width: 600px;
  margin: 0 auto;
}

/* 统计卡片 */
.stats {
  display: flex;
  justify-content: center;
  gap: 40px;
  margin-top: 40px;
  flex-wrap: wrap;
}

.stat-item {
  text-align: center;
  padding: 24px 40px;
  background: var(--bg-primary);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-sm);
  min-width: 140px;
}

.stat-value {
  font-size: 36px;
  font-weight: 700;
  color: var(--accent-color);
}

.stat-label {
  font-size: 14px;
  color: var(--text-secondary);
  margin-top: 4px;
}

/* 内容区域 */
.section {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 48px 24px;
}

.section-title {
  font-size: 24px;
  font-weight: 600;
  margin-bottom: 24px;
  display: flex;
  align-items: center;
  gap: 12px;
}

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

/* 卡片网格 */
.card-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
  gap: 24px;
}

.card {
  background: var(--bg-primary);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-lg);
  padding: 24px;
  transition: all 0.2s;
}

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

.card-title {
  font-size: 18px;
  font-weight: 600;
  margin-bottom: 8px;
  color: var(--text-primary);
}

.card-meta {
  font-size: 13px;
  color: var(--text-muted);
  margin-bottom: 12px;
}

.card-desc {
  font-size: 14px;
  color: var(--text-secondary);
  line-height: 1.6;
}

/* 进度条 */
.progress-bar {
  margin-top: 16px;
}

.progress-label {
  display: flex;
  justify-content: space-between;
  font-size: 13px;
  color: var(--text-secondary);
  margin-bottom: 6px;
}

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

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

/* 列表 */
.list {
  background: var(--bg-primary);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-lg);
  overflow: hidden;
}

.list-item {
  padding: 16px 20px;
  border-bottom: 1px solid var(--border-color);
  display: flex;
  align-items: center;
  gap: 12px;
  transition: background 0.2s;
}

.list-item:last-child {
  border-bottom: none;
}

.list-item:hover {
  background: var(--bg-secondary);
}

.list-item-icon {
  width: 40px;
  height: 40px;
  background: var(--bg-tertiary);
  border-radius: var(--radius-md);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 18px;
  flex-shrink: 0;
}

.list-item-content {
  flex: 1;
}

.list-item-title {
  font-weight: 500;
  color: var(--text-primary);
  margin-bottom: 2px;
}

.list-item-meta {
  font-size: 13px;
  color: var(--text-muted);
}

.list-item-status {
  font-size: 12px;
  padding: 4px 10px;
  border-radius: 12px;
  font-weight: 500;
}

.status-completed {
  background: #c6f6d5;
  color: #276749;
}

.status-reading {
  background: #bee3f8;
  color: #2c5282;
}

.status-todo {
  background: var(--bg-tertiary);
  color: var(--text-secondary);
}

/* 三栏布局 */
.three-col {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 24px;
}

.col-section {
  background: var(--bg-secondary);
  border-radius: var(--radius-lg);
  padding: 20px;
}

.col-title {
  font-size: 16px;
  font-weight: 600;
  margin-bottom: 16px;
  padding-bottom: 12px;
  border-bottom: 1px solid var(--border-color);
}

.col-list {
  list-style: none;
}

.col-list li {
  padding: 10px 0;
  border-bottom: 1px solid var(--border-color);
}

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

.col-list a {
  color: var(--text-primary);
  font-size: 14px;
  display: block;
}

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

/* 分类筛选 */
.filter-bar {
  display: flex;
  gap: 12px;
  margin-bottom: 24px;
  flex-wrap: wrap;
}

.filter-btn {
  padding: 8px 16px;
  border: 1px solid var(--border-color);
  border-radius: 20px;
  background: var(--bg-primary);
  color: var(--text-secondary);
  font-size: 14px;
  cursor: pointer;
  transition: all 0.2s;
}

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

/* 文章详情 */
.article-header {
  text-align: center;
  padding: 40px 24px;
  background: var(--bg-secondary);
}

.article-title {
  font-size: 32px;
  font-weight: 700;
  margin-bottom: 16px;
}

.article-meta {
  display: flex;
  justify-content: center;
  gap: 24px;
  color: var(--text-secondary);
  font-size: 14px;
}

.article-meta span {
  display: flex;
  align-items: center;
  gap: 6px;
}

.article-content {
  max-width: 800px;
  margin: 0 auto;
  padding: 48px 24px;
}

.article-content h2 {
  font-size: 24px;
  font-weight: 600;
  margin: 40px 0 20px;
  padding-bottom: 12px;
  border-bottom: 2px solid var(--border-color);
}

.article-content h3 {
  font-size: 20px;
  font-weight: 600;
  margin: 32px 0 16px;
}

.article-content p {
  margin-bottom: 16px;
  color: var(--text-secondary);
  line-height: 1.8;
}

.article-content ul,
.article-content ol {
  margin-bottom: 16px;
  padding-left: 24px;
  color: var(--text-secondary);
}

.article-content li {
  margin-bottom: 8px;
}

/* 提示框 */
.tip-box {
  background: #e6fffa;
  border-left: 4px solid var(--accent-color);
  padding: 16px 20px;
  margin: 24px 0;
  border-radius: 0 var(--radius-md) var(--radius-md) 0;
}

.tip-box-title {
  font-weight: 600;
  color: #234e52;
  margin-bottom: 8px;
}

.tip-box p {
  color: #285e61;
  margin: 0;
}

/* 练习框 */
.exercise-box {
  background: var(--bg-secondary);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-lg);
  padding: 24px;
  margin: 24px 0;
}

.exercise-title {
  font-weight: 600;
  margin-bottom: 12px;
  display: flex;
  align-items: center;
  gap: 8px;
}

/* 404页面 */
.error-page {
  min-height: calc(100vh - var(--header-height) - 200px);
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  text-align: center;
  padding: 48px 24px;
}

.error-code {
  font-size: 120px;
  font-weight: 700;
  color: var(--accent-color);
  line-height: 1;
  margin-bottom: 16px;
}

.error-title {
  font-size: 28px;
  font-weight: 600;
  margin-bottom: 12px;
}

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

.btn {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 12px 24px;
  background: var(--accent-color);
  color: white;
  border-radius: var(--radius-md);
  font-weight: 500;
  transition: all 0.2s;
}

.btn:hover {
  background: var(--accent-dark);
  color: white;
  transform: translateY(-1px);
  box-shadow: var(--shadow-md);
}

/* 页脚 */
.footer {
  background: var(--bg-secondary);
  border-top: 1px solid var(--border-color);
  padding: 48px 24px 24px;
  margin-top: 48px;
}

.footer-inner {
  max-width: var(--max-width);
  margin: 0 auto;
}

.footer-grid {
  display: grid;
  grid-template-columns: 2fr 1fr 1fr 1fr;
  gap: 48px;
  margin-bottom: 48px;
}

.footer-brand p {
  color: var(--text-secondary);
  font-size: 14px;
  line-height: 1.6;
  margin-top: 12px;
}

.footer-title {
  font-size: 14px;
  font-weight: 600;
  margin-bottom: 16px;
  text-transform: uppercase;
  letter-spacing: 0.5px;
}

.footer-links {
  list-style: none;
}

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

.footer-links a {
  color: var(--text-secondary);
  font-size: 14px;
}

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

.footer-bottom {
  border-top: 1px solid var(--border-color);
  padding-top: 24px;
  text-align: center;
  color: var(--text-muted);
  font-size: 14px;
}

/* 响应式设计 */
@media (max-width: 1024px) {
  .three-col {
    grid-template-columns: repeat(2, 1fr);
  }

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

@media (max-width: 768px) {
  .header-inner {
    flex-wrap: wrap;
    padding: 0 16px;
  }

  .nav {
    display: none;
  }

  .search-box input {
    width: 160px;
  }

  .hero {
    padding: 40px 16px;
  }

  .hero h1 {
    font-size: 28px;
  }

  .stats {
    gap: 16px;
  }

  .stat-item {
    padding: 16px 24px;
    min-width: 100px;
  }

  .stat-value {
    font-size: 28px;
  }

  .section {
    padding: 32px 16px;
  }

  .three-col {
    grid-template-columns: 1fr;
  }

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

  .article-title {
    font-size: 24px;
  }

  .article-meta {
    flex-wrap: wrap;
    gap: 12px;
  }

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

  .error-code {
    font-size: 80px;
  }
}

@media (max-width: 480px) {
  .hero h1 {
    font-size: 24px;
  }

  .section-title {
    font-size: 20px;
  }

  .filter-bar {
    gap: 8px;
  }

  .filter-btn {
    padding: 6px 12px;
    font-size: 13px;
  }
}