:root {
  --accent-color: #009688;
  --accent-light: #e0f2f1;
  --text-primary: #333;
  --text-secondary: #666;
  --text-muted: #999;
  --bg-primary: #fff;
  --bg-secondary: #f5f5f5;
  --border-color: #e0e0e0;
  --shadow: 0 2px 8px rgba(0,0,0,0.1);
  --radius: 8px;
  --max-width: 1200px;
  --header-height: 60px;
}

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

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

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

a:hover {
  text-decoration: underline;
}

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

.header-inner {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 20px;
  height: 100%;
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.logo {
  font-size: 1.5rem;
  font-weight: 700;
  color: var(--accent-color);
}

.nav {
  display: flex;
  gap: 30px;
}

.nav a {
  color: var(--text-primary);
  font-weight: 500;
}

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

.search-box {
  display: flex;
  align-items: center;
  gap: 8px;
}

.search-box input {
  padding: 8px 12px;
  border: 1px solid var(--border-color);
  border-radius: var(--radius);
  width: 200px;
}

.search-box button {
  padding: 8px 16px;
  background: var(--accent-color);
  color: white;
  border: none;
  border-radius: var(--radius);
  cursor: pointer;
}

/* Main Container */
.container {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 40px 20px;
}

/* Hero Section */
.hero {
  text-align: center;
  padding: 60px 20px;
  background: linear-gradient(135deg, var(--accent-light) 0%, var(--bg-primary) 100%);
  border-radius: var(--radius);
  margin-bottom: 40px;
}

.hero h1 {
  font-size: 2.5rem;
  margin-bottom: 16px;
  color: var(--text-primary);
}

.hero p {
  font-size: 1.2rem;
  color: var(--text-secondary);
  max-width: 600px;
  margin: 0 auto;
}

/* Section Title */
.section-title {
  font-size: 1.5rem;
  margin-bottom: 24px;
  padding-bottom: 12px;
  border-bottom: 2px solid var(--accent-color);
  display: inline-block;
}

/* Guide Categories */
.categories {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 20px;
  margin-bottom: 40px;
}

.category-card {
  background: var(--bg-primary);
  border: 1px solid var(--border-color);
  border-radius: var(--radius);
  padding: 30px;
  text-align: center;
  transition: all 0.3s;
}

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

.category-card h3 {
  color: var(--accent-color);
  margin-bottom: 8px;
}

.category-card p {
  color: var(--text-secondary);
  font-size: 0.9rem;
}

/* Guide List */
.guide-list {
  display: flex;
  flex-direction: column;
  gap: 16px;
  margin-bottom: 40px;
}

.guide-item {
  display: flex;
  align-items: center;
  gap: 20px;
  padding: 20px;
  background: var(--bg-primary);
  border: 1px solid var(--border-color);
  border-radius: var(--radius);
  transition: all 0.3s;
}

.guide-item:hover {
  box-shadow: var(--shadow);
}

.step-number {
  width: 48px;
  height: 48px;
  background: var(--accent-color);
  color: white;
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  font-weight: 700;
  font-size: 1.2rem;
  flex-shrink: 0;
}

.guide-content {
  flex: 1;
}

.guide-content h4 {
  margin-bottom: 4px;
}

.guide-content p {
  color: var(--text-secondary);
  font-size: 0.9rem;
}

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

/* Article Grid */
.article-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 30px;
  margin-bottom: 40px;
}

.article-column h3 {
  font-size: 1.1rem;
  margin-bottom: 16px;
  color: var(--accent-color);
}

.article-column ul {
  list-style: none;
}

.article-column li {
  padding: 8px 0;
  border-bottom: 1px solid var(--border-color);
}

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

.article-column a {
  color: var(--text-primary);
}

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

/* Breadcrumb */
.breadcrumb {
  padding: 16px 20px;
  background: var(--bg-secondary);
  margin-bottom: 30px;
  border-radius: var(--radius);
}

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

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

/* Category Header */
.category-header {
  text-align: center;
  padding: 40px 20px;
  background: var(--bg-secondary);
  border-radius: var(--radius);
  margin-bottom: 30px;
}

.category-header h1 {
  font-size: 2rem;
  margin-bottom: 8px;
}

.category-header p {
  color: var(--text-secondary);
}

/* Difficulty Badge */
.difficulty {
  display: inline-flex;
  align-items: center;
  gap: 4px;
  padding: 4px 12px;
  border-radius: 20px;
  font-size: 0.85rem;
  font-weight: 500;
}

.difficulty.easy {
  background: #e8f5e9;
  color: #2e7d32;
}

.difficulty.medium {
  background: #fff3e0;
  color: #ef6c00;
}

.difficulty.hard {
  background: #ffebee;
  color: #c62828;
}

/* Pagination */
.pagination {
  display: flex;
  justify-content: center;
  gap: 8px;
  margin: 40px 0;
}

.pagination a,
.pagination span {
  padding: 8px 16px;
  border: 1px solid var(--border-color);
  border-radius: var(--radius);
  color: var(--text-primary);
}

.pagination a:hover {
  background: var(--accent-color);
  color: white;
  border-color: var(--accent-color);
}

.pagination .current {
  background: var(--accent-color);
  color: white;
  border-color: var(--accent-color);
}

/* Article Detail */
.article-header {
  margin-bottom: 30px;
}

.article-header h1 {
  font-size: 2rem;
  margin-bottom: 16px;
}

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

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

.featured-image {
  width: 100%;
  height: 400px;
  background: var(--bg-secondary);
  border-radius: var(--radius);
  display: flex;
  align-items: center;
  justify-content: center;
  color: var(--text-muted);
  margin-bottom: 30px;
}

/* Steps Overview */
.steps-overview {
  background: var(--bg-secondary);
  padding: 30px;
  border-radius: var(--radius);
  margin-bottom: 30px;
}

.steps-overview h3 {
  margin-bottom: 20px;
}

.step-item {
  display: flex;
  align-items: center;
  gap: 16px;
  padding: 16px;
  background: var(--bg-primary);
  border-radius: var(--radius);
  margin-bottom: 12px;
}

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

.step-item.completed {
  border-left: 4px solid var(--accent-color);
}

.step-item.active {
  border-left: 4px solid #ff9800;
}

.step-item.pending {
  border-left: 4px solid var(--border-color);
}

.step-status {
  width: 24px;
  height: 24px;
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 0.75rem;
  flex-shrink: 0;
}

.step-item.completed .step-status {
  background: var(--accent-color);
  color: white;
}

.step-item.active .step-status {
  background: #ff9800;
  color: white;
}

.step-item.pending .step-status {
  background: var(--border-color);
  color: var(--text-muted);
}

/* Article Content */
.article-content {
  line-height: 1.8;
  margin-bottom: 40px;
}

.article-content h2 {
  font-size: 1.5rem;
  margin: 30px 0 16px;
  padding-bottom: 8px;
  border-bottom: 1px solid var(--border-color);
}

.article-content h3 {
  font-size: 1.25rem;
  margin: 24px 0 12px;
  color: var(--accent-color);
}

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

/* Tip Box */
.tip-box {
  background: var(--accent-light);
  border-left: 4px solid var(--accent-color);
  padding: 20px;
  border-radius: 0 var(--radius) var(--radius) 0;
  margin: 20px 0;
}

.tip-box h4 {
  color: var(--accent-color);
  margin-bottom: 8px;
}

.tip-box p {
  margin: 0;
  color: var(--text-secondary);
}

/* Checklist */
.checklist {
  list-style: none;
  margin: 20px 0;
}

.checklist li {
  padding: 8px 0 8px 32px;
  position: relative;
}

.checklist li::before {
  content: '☐';
  position: absolute;
  left: 0;
  color: var(--accent-color);
  font-weight: bold;
}

/* 404 Page */
.error-page {
  text-align: center;
  padding: 80px 20px;
}

.error-code {
  font-size: 8rem;
  font-weight: 700;
  color: var(--accent-color);
  line-height: 1;
  margin-bottom: 20px;
}

.error-page h1 {
  font-size: 2rem;
  margin-bottom: 16px;
}

.error-page p {
  color: var(--text-secondary);
  margin-bottom: 30px;
}

.btn {
  display: inline-block;
  padding: 12px 32px;
  background: var(--accent-color);
  color: white;
  border-radius: var(--radius);
  font-weight: 500;
  transition: all 0.3s;
}

.btn:hover {
  background: #00796b;
  text-decoration: none;
}

/* Footer */
.footer {
  background: var(--bg-secondary);
  padding: 40px 20px;
  margin-top: 60px;
  border-top: 1px solid var(--border-color);
}

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

.footer p {
  color: var(--text-secondary);
  margin-bottom: 8px;
}

.footer-links {
  display: flex;
  justify-content: center;
  gap: 24px;
  margin-top: 16px;
}

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

/* Responsive */
@media (max-width: 768px) {
  .header-inner {
    flex-wrap: wrap;
    height: auto;
    padding: 12px 16px;
  }

  .nav {
    order: 3;
    width: 100%;
    justify-content: center;
    margin-top: 12px;
    gap: 16px;
  }

  .search-box {
    display: none;
  }

  .hero h1 {
    font-size: 1.75rem;
  }

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

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

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

  .guide-item {
    flex-direction: column;
    text-align: center;
  }

  .guide-meta {
    justify-content: center;
  }

  .featured-image {
    height: 200px;
  }

  .article-meta {
    flex-wrap: wrap;
  }

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

@media (max-width: 480px) {
  .container {
    padding: 20px 16px;
  }

  .hero {
    padding: 40px 16px;
  }

  .category-card {
    padding: 20px;
  }

  .step-item {
    flex-direction: column;
    text-align: center;
  }
}