:root {
  --primary-blue: #256DB1;
  --secondary-blue: #1E5A96;
  --primary-orange: #FF8C00;
  --light-orange: #FFF3E0;
  --text-dark: #2C3E50;
  --text-medium: #34495E;
  --text-light: #7F8C8D;
  --bg-white: #FFFFFF;
  --bg-light: #F8F9FA;
  --border-light: #E9ECEF;
}

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

body {
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', system-ui, sans-serif;
  line-height: 1.6;
  color: var(--text-dark);
  background-color: var(--bg-light);
  font-size: 16px;
}

.progress-bar {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  height: 4px;
  background: var(--border-light);
  z-index: 1000;
}

.progress-fill {
  height: 100%;
  background: linear-gradient(90deg, var(--primary-blue), var(--primary-orange));
  width: 0%;
  transition: width 0.3s ease;
}

.layout-container {
  display: flex;
  max-width: 1100px;
  margin: 0 auto;
  min-height: 100vh;
  background: var(--bg-white);
  box-shadow: 0 0 20px rgba(0, 0, 0, 0.1);
}

.sidebar {
  width: 280px;
  background: var(--bg-light);
  border-right: 1px solid var(--border-light);
  position: sticky;
  top: 0;
  height: 100vh;
  overflow-y: auto;
  padding: 2rem 0;
}

.sidebar-content {
  padding: 0 1.5rem;
}

.back-link {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  padding: 0.5rem 1rem;
  background: var(--primary-blue);
  color: var(--bg-white);
  text-decoration: none;
  border-radius: 4px;
  font-size: 0.9rem;
  font-weight: 500;
  margin-bottom: 2rem;
  transition: background-color 0.2s;
  width: 100%;
  justify-content: center;
}

.back-link:hover {
  background: var(--secondary-blue);
}

.toc-title {
  font-size: 1.1rem;
  font-weight: 600;
  color: var(--text-dark);
  margin-bottom: 1rem;
  padding-bottom: 0.5rem;
  border-bottom: 2px solid var(--primary-blue);
}

.toc-list {
  list-style: none;
  padding: 0;
}

.toc-item {
  margin-bottom: 0.5rem;
}

.toc-link {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  padding: 0.5rem;
  color: var(--text-medium);
  text-decoration: none;
  border-radius: 4px;
  transition: all 0.2s;
  font-size: 0.9rem;
}

.toc-link:hover {
  background: var(--light-orange);
  color: var(--primary-orange);
}

.toc-link.active {
  background: var(--primary-blue);
  color: var(--bg-white);
}

.toc-number {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 24px;
  height: 24px;
  background: var(--border-light);
  color: var(--text-medium);
  border-radius: 50%;
  font-size: 0.8rem;
  font-weight: 600;
  flex-shrink: 0;
}

.toc-link.active .toc-number {
  background: var(--primary-orange);
  color: var(--bg-white);
}

.toc-section {
  margin-top: 1.5rem;
}

.toc-section-title {
  font-size: 0.85rem;
  font-weight: 600;
  color: var(--primary-blue);
  margin-bottom: 0.75rem;
  padding-left: 0.5rem;
  text-transform: uppercase;
  letter-spacing: 0.5px;
}

.toc-section .toc-list {
  margin-left: 0.5rem;
}

.main-content {
  flex: 1;
  overflow-x: hidden;
}

.article-header {
  padding: 3rem 3rem 0rem;
  border-bottom: 1px solid var(--border-light);
}

.article-meta {
  color: var(--text-light);
  font-size: 0.9rem;
  margin-bottom: 1rem;
}

.article-title {
  font-size: 2.5rem;
  font-weight: 700;
  color: var(--primary-blue);
  margin-bottom: 1rem;
  line-height: 1.2;
}

.article-subtitle {
  font-size: 1.2rem;
  color: var(--text-medium);
  font-weight: 400;
  line-height: 1.5;
}

.article-content {
  padding: 2rem 3rem 3rem;
}

.intro-section {
  background: var(--light-orange);
  border-left: 4px solid var(--primary-orange);
  padding: 1rem;
  margin-bottom: 1.5rem;
  border-radius: 0 4px 4px 0;
}

.intro-section h3 {
  color: var(--primary-orange);
  font-size: 1rem;
  margin-bottom: 0.5rem;
  font-weight: 600;
}

.intro-section p {
  font-size: 0.95rem;
  color: var(--text-medium);
}

.section-header {
  font-size: 1.8rem;
  color: var(--text-dark);
  margin: 2rem 0 1.5rem 0;
  font-weight: 600;
  border-bottom: 2px solid var(--primary-blue);
  padding-bottom: 0.5rem;
}

.step-article {
  margin-bottom: 1.5rem;
  padding-bottom: 0.5rem;
  border-bottom: 1px solid var(--border-light);
  scroll-margin-top: 2rem;
}

.step-article:last-child {
  border-bottom: none;
  margin-bottom: 0;
}

.step-header {
  display: flex;
  align-items: baseline;
  gap: 1rem;
  margin-bottom: 1rem;
}

.step-number {
  flex-shrink: 0;
  width: 35px;
  height: 35px;
  background: var(--primary-blue);
  color: var(--bg-white);
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  font-weight: 700;
  font-size: 1rem;
}

.step-title {
  font-size: 1.4rem;
  color: var(--text-dark);
  font-weight: 600;
}

.step-content {
  margin-left: 0px;
}

.step-content p {
  font-size: 1rem;
  margin-bottom: 0.5rem;
  color: var(--text-medium);
}

.step-list {
  list-style: none;
  padding: 0;
}

.step-list li {
  position: relative;
  padding-left: 1.5rem;
  margin-bottom: 0.5rem;
  font-size: 1rem;
  color: var(--text-medium);
  line-height: 1.6;
}

.step-list li::before {
  content: '•';
  position: absolute;
  left: 0;
  color: var(--primary-orange);
  font-weight: bold;
  font-size: 1.2rem;
  top: 0;
}

/* Image styling */
.step-content img {
  max-width: 100%;
  height: auto;
  border-radius: 8px;
  margin: 1rem 0;
  box-shadow: 0 4px 12px rgba(0, 0, 0, 0.1);
}

/* Responsive Design */
@media (max-width: 1024px) {
  .sidebar {
    width: 240px;
  }

  .sidebar-content {
    padding: 0 1rem;
  }
}

@media (max-width: 768px) {
  .layout-container {
    flex-direction: column;
  }

  .sidebar {
    display: none;
  }

  .main-content {
    width: 100%;
  }

  .article-header {
    padding: 2rem 1.5rem 1.5rem;
  }

  .article-content {
    padding: 1.5rem;
  }

  .article-title {
    font-size: 2rem;
  }

  .article-subtitle {
    font-size: 1.1rem;
  }

  .section-header {
    font-size: 1.5rem;
  }

  .step-title {
    font-size: 1.2rem;
  }

  .step-content {
    margin-left: 0;
    margin-top: 1rem;
  }

  .step-header {
    flex-direction: column;
    align-items: flex-start;
    gap: 0.75rem;
  }

  .step-list {
    margin-left: 0;
  }

  .step-list li {
    margin-left: 0;
  }
}

/* No loading animations - immediate display */
.step-article {
  opacity: 1;
  transform: translateY(0);
}