/* ===== CSS Variables / Design Tokens ===== */
:root {
  --primary: #2D3A8C;
  --primary-dark: #1E2A6E;
  --primary-light: #3B4CB8;
  --accent: #4F5BD5;
  --bg: #FFFFFF;
  --bg-light: #F7F8FC;
  --bg-card: #FFFFFF;
  --text-primary: #1A1A2E;
  --text-secondary: #6B7280;
  --text-muted: #9CA3AF;
  --border: #E5E7EB;
  --border-light: #F3F4F6;
  --shadow-sm: 0 1px 2px rgba(0,0,0,0.05);
  --shadow-md: 0 4px 6px -1px rgba(0,0,0,0.07), 0 2px 4px -1px rgba(0,0,0,0.04);
  --shadow-lg: 0 10px 15px -3px rgba(0,0,0,0.08), 0 4px 6px -2px rgba(0,0,0,0.04);
  --shadow-xl: 0 20px 25px -5px rgba(0,0,0,0.08), 0 10px 10px -5px rgba(0,0,0,0.03);
  --radius-sm: 6px;
  --radius-md: 10px;
  --radius-lg: 16px;
  --radius-xl: 24px;
  --radius-full: 9999px;
  --font-sans: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, "Noto Sans SC", sans-serif;
  --transition: all 0.2s ease;
}

/* ===== Reset & Base ===== */
*, *::before, *::after {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
  font-size: 16px;
}

body {
  font-family: var(--font-sans);
  color: var(--text-primary);
  background: var(--bg);
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

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

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

/* ===== Navbar ===== */
.navbar {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 1000;
  background: rgba(255,255,255,0.95);
  backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--border-light);
  height: 64px;
  display: flex;
  align-items: center;
  padding: 0 24px;
}

.navbar-inner {
  max-width: 1200px;
  margin: 0 auto;
  width: 100%;
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.navbar-brand {
  display: flex;
  align-items: center;
  gap: 10px;
  font-size: 18px;
  font-weight: 700;
  color: var(--primary);
}

.navbar-brand svg {
  width: 28px;
  height: 28px;
}

.navbar-nav {
  display: flex;
  align-items: center;
  gap: 8px;
}

.nav-link {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 8px 16px;
  font-size: 14px;
  color: var(--text-secondary);
  border-radius: var(--radius-full);
  transition: var(--transition);
}

.nav-link:hover {
  color: var(--primary);
  background: var(--bg-light);
}

.nav-link svg {
  width: 16px;
  height: 16px;
}

.btn-nav-primary {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 8px 20px;
  font-size: 14px;
  font-weight: 600;
  color: #fff;
  background: var(--primary);
  border-radius: var(--radius-full);
  border: none;
  cursor: pointer;
  transition: var(--transition);
}

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

.btn-nav-primary svg {
  width: 16px;
  height: 16px;
}

/* ===== Hero Section ===== */
.hero {
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  text-align: center;
  padding: 120px 24px 80px;
  background: var(--bg);
}

.hero-badge {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 6px 16px;
  background: var(--bg-light);
  border: 1px solid var(--border);
  border-radius: var(--radius-full);
  font-size: 13px;
  color: var(--text-secondary);
  margin-bottom: 32px;
}

.hero-badge svg {
  width: 16px;
  height: 16px;
  color: #F59E0B;
}

.hero h1 {
  font-size: 48px;
  font-weight: 800;
  line-height: 1.2;
  color: var(--primary);
  margin-bottom: 20px;
  letter-spacing: -0.5px;
}

.hero h1 span {
  display: block;
  color: var(--text-primary);
  font-size: 40px;
}

.hero-desc {
  font-size: 16px;
  color: var(--text-secondary);
  max-width: 520px;
  margin: 0 auto 40px;
  line-height: 1.8;
}

.hero-actions {
  display: flex;
  align-items: center;
  gap: 16px;
  justify-content: center;
  flex-wrap: wrap;
}

.btn-primary {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 14px 32px;
  font-size: 15px;
  font-weight: 600;
  color: #fff;
  background: var(--primary);
  border-radius: var(--radius-full);
  border: none;
  cursor: pointer;
  transition: var(--transition);
}

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

.btn-primary svg {
  width: 18px;
  height: 18px;
}

.btn-outline {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 14px 32px;
  font-size: 15px;
  font-weight: 600;
  color: var(--text-secondary);
  background: var(--bg);
  border: 1.5px solid var(--border);
  border-radius: var(--radius-full);
  cursor: pointer;
  transition: var(--transition);
}

.btn-outline:hover {
  border-color: var(--primary);
  color: var(--primary);
  transform: translateY(-2px);
  box-shadow: var(--shadow-md);
}

.btn-outline svg {
  width: 18px;
  height: 18px;
}

/* ===== Section Common ===== */
.section {
  padding: 80px 24px;
}

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

.section-title {
  font-size: 32px;
  font-weight: 800;
  text-align: center;
  margin-bottom: 16px;
  color: var(--text-primary);
}

.section-subtitle {
  font-size: 16px;
  color: var(--text-secondary);
  text-align: center;
  max-width: 600px;
  margin: 0 auto 48px;
  line-height: 1.7;
}

/* ===== Skills Grid ===== */
.skills-grid {
  max-width: 1200px;
  margin: 0 auto;
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 24px;
}

.skill-card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 32px;
  transition: var(--transition);
  cursor: pointer;
  text-decoration: none;
  display: block;
}

.skill-card:hover {
  border-color: var(--primary);
  box-shadow: var(--shadow-xl);
  transform: translateY(-4px);
}

.skill-card-icon {
  width: 56px;
  height: 56px;
  border-radius: var(--radius-md);
  display: flex;
  align-items: center;
  justify-content: center;
  margin-bottom: 20px;
  font-size: 28px;
}

.skill-card-icon.blue {
  background: #EEF0FF;
  color: var(--primary);
}

.skill-card-icon.green {
  background: #ECFDF5;
  color: #059669;
}

.skill-card-icon.orange {
  background: #FFF7ED;
  color: #EA580C;
}

.skill-card h3 {
  font-size: 20px;
  font-weight: 700;
  margin-bottom: 8px;
  color: var(--text-primary);
}

.skill-card p {
  font-size: 14px;
  color: var(--text-secondary);
  line-height: 1.7;
  margin-bottom: 16px;
}

.skill-card-tags {
  display: flex;
  flex-wrap: wrap;
  gap: 6px;
}

.skill-tag {
  display: inline-block;
  padding: 4px 10px;
  font-size: 12px;
  color: var(--text-muted);
  background: var(--bg-light);
  border-radius: var(--radius-full);
  border: 1px solid var(--border-light);
}

/* ===== Steps Section ===== */
.steps-grid {
  max-width: 1000px;
  margin: 0 auto;
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 40px;
  text-align: center;
}

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

.step-icon {
  width: 72px;
  height: 72px;
  border-radius: var(--radius-lg);
  background: var(--bg-light);
  display: flex;
  align-items: center;
  justify-content: center;
  margin-bottom: 20px;
  font-size: 36px;
}

.step-item h3 {
  font-size: 18px;
  font-weight: 700;
  margin-bottom: 8px;
}

.step-item p {
  font-size: 14px;
  color: var(--text-secondary);
  line-height: 1.6;
}

/* ===== Features Section ===== */
.features-grid {
  max-width: 1200px;
  margin: 0 auto;
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(200px, 1fr));
  gap: 20px;
}

.feature-card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 24px;
  text-align: center;
  transition: var(--transition);
}

.feature-card:hover {
  box-shadow: var(--shadow-md);
  transform: translateY(-2px);
}

.feature-card-icon {
  font-size: 36px;
  margin-bottom: 12px;
}

.feature-card h4 {
  font-size: 15px;
  font-weight: 700;
  margin-bottom: 6px;
}

.feature-card p {
  font-size: 13px;
  color: var(--text-secondary);
  line-height: 1.5;
}

/* ===== Skill Detail Page ===== */
.page-header {
  padding: 100px 24px 40px;
  text-align: center;
  background: var(--bg-light);
}

.page-header .back-link {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  font-size: 14px;
  color: var(--text-secondary);
  margin-bottom: 24px;
}

.page-header .back-link:hover {
  color: var(--primary);
}

.page-header h1 {
  font-size: 36px;
  font-weight: 800;
  margin-bottom: 12px;
}

.page-header .desc {
  font-size: 16px;
  color: var(--text-secondary);
  max-width: 600px;
  margin: 0 auto 24px;
  line-height: 1.7;
}

.page-header .meta {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 24px;
  font-size: 13px;
  color: var(--text-muted);
}

.page-header .meta span {
  display: inline-flex;
  align-items: center;
  gap: 4px;
}

/* ===== Content Area ===== */
.content-area {
  max-width: 900px;
  margin: 0 auto;
  padding: 48px 24px 80px;
}

.content-area h2 {
  font-size: 24px;
  font-weight: 700;
  margin: 40px 0 16px;
  padding-bottom: 8px;
  border-bottom: 2px solid var(--border-light);
}

.content-area h3 {
  font-size: 18px;
  font-weight: 600;
  margin: 24px 0 12px;
}

.content-area p {
  font-size: 15px;
  color: var(--text-secondary);
  line-height: 1.8;
  margin-bottom: 16px;
}

.content-area ul, .content-area ol {
  margin: 0 0 16px 24px;
  color: var(--text-secondary);
  font-size: 15px;
  line-height: 1.8;
}

.content-area li {
  margin-bottom: 6px;
}

.content-area code {
  background: var(--bg-light);
  padding: 2px 6px;
  border-radius: 4px;
  font-size: 13px;
  color: var(--primary);
}

.content-area pre {
  background: #1E293B;
  color: #E2E8F0;
  padding: 20px;
  border-radius: var(--radius-md);
  overflow-x: auto;
  margin-bottom: 20px;
  font-size: 13px;
  line-height: 1.6;
}

.content-area pre code {
  background: none;
  color: inherit;
  padding: 0;
}

.content-area table {
  width: 100%;
  border-collapse: collapse;
  margin-bottom: 20px;
  font-size: 14px;
}

.content-area table th,
.content-area table td {
  padding: 12px 16px;
  text-align: left;
  border-bottom: 1px solid var(--border);
}

.content-area table th {
  background: var(--bg-light);
  font-weight: 600;
  color: var(--text-primary);
}

.content-area table td {
  color: var(--text-secondary);
}

/* ===== Interactive Demo Sections ===== */
.demo-section {
  max-width: 900px;
  margin: 0 auto;
  padding: 48px 24px 80px;
}

.demo-card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 32px;
  margin-bottom: 24px;
}

.demo-card h3 {
  font-size: 18px;
  font-weight: 700;
  margin-bottom: 16px;
  display: flex;
  align-items: center;
  gap: 8px;
}

.form-group {
  margin-bottom: 20px;
}

.form-group label {
  display: block;
  font-size: 14px;
  font-weight: 600;
  margin-bottom: 6px;
  color: var(--text-primary);
}

.form-group input,
.form-group select,
.form-group textarea {
  width: 100%;
  padding: 10px 14px;
  font-size: 14px;
  border: 1.5px solid var(--border);
  border-radius: var(--radius-sm);
  background: var(--bg);
  color: var(--text-primary);
  font-family: var(--font-sans);
  transition: var(--transition);
}

.form-group input:focus,
.form-group select:focus,
.form-group textarea:focus {
  outline: none;
  border-color: var(--primary);
  box-shadow: 0 0 0 3px rgba(45,58,140,0.1);
}

.form-group textarea {
  min-height: 100px;
  resize: vertical;
}

.form-row {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 16px;
}

.btn-submit {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 12px 28px;
  font-size: 15px;
  font-weight: 600;
  color: #fff;
  background: var(--primary);
  border-radius: var(--radius-sm);
  border: none;
  cursor: pointer;
  transition: var(--transition);
}

.btn-submit:hover {
  background: var(--primary-dark);
  box-shadow: var(--shadow-md);
}

.btn-submit:disabled {
  opacity: 0.6;
  cursor: not-allowed;
}

/* ===== Result Area - Improved ===== */
.result-area {
  margin-top: 24px;
  background: var(--bg);
  border-radius: var(--radius-lg);
  border: 1px solid var(--border);
  display: none;
  overflow: hidden;
}

.result-area.show {
  display: block;
  animation: slideDown 0.3s ease;
}

@keyframes slideDown {
  from {
    opacity: 0;
    transform: translateY(-10px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

.result-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 16px 24px;
  background: var(--bg-light);
  border-bottom: 1px solid var(--border);
}

.result-header h4 {
  font-size: 15px;
  font-weight: 700;
  color: var(--text-primary);
  display: flex;
  align-items: center;
  gap: 8px;
  margin: 0;
}

.result-header h4 svg {
  color: var(--primary);
}

.result-copy-btn {
  display: inline-flex;
  align-items: center;
  gap: 4px;
  padding: 6px 14px;
  font-size: 13px;
  font-weight: 500;
  color: var(--text-secondary);
  background: var(--bg);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  cursor: pointer;
  transition: var(--transition);
}

.result-copy-btn:hover {
  color: var(--primary);
  border-color: var(--primary);
}

.result-copy-btn.copied {
  color: #059669;
  border-color: #059669;
}

.result-content {
  padding: 24px;
  max-height: 600px;
  overflow-y: auto;
}

.result-error {
  display: flex;
  align-items: center;
  gap: 8px;
  padding: 16px 24px;
  color: #DC2626;
  font-size: 14px;
}

.result-error svg {
  flex-shrink: 0;
}

/* ===== Markdown Content Styles ===== */
.md-content {
  font-size: 14px;
  line-height: 1.8;
  color: var(--text-primary);
}

.md-content .md-h1 {
  font-size: 22px;
  font-weight: 700;
  margin: 28px 0 12px;
  padding-bottom: 8px;
  border-bottom: 2px solid var(--border-light);
  color: var(--text-primary);
}

.md-content .md-h2 {
  font-size: 18px;
  font-weight: 700;
  margin: 24px 0 10px;
  color: var(--text-primary);
}

.md-content .md-h3 {
  font-size: 16px;
  font-weight: 600;
  margin: 20px 0 8px;
  color: var(--text-primary);
}

.md-content .md-h4 {
  font-size: 14px;
  font-weight: 600;
  margin: 16px 0 6px;
  color: var(--text-primary);
}

.md-content .md-p {
  margin: 0 0 8px;
  color: var(--text-secondary);
  line-height: 1.8;
}

.md-content strong {
  color: var(--text-primary);
  font-weight: 600;
}

.md-content em {
  font-style: italic;
}

.md-content .md-hr {
  border: none;
  border-top: 1px solid var(--border);
  margin: 20px 0;
}

.md-content .md-ul,
.md-content .md-ol {
  margin: 8px 0 12px 20px;
  padding: 0;
}

.md-content .md-ul li,
.md-content .md-ol li {
  margin-bottom: 4px;
  color: var(--text-secondary);
  line-height: 1.7;
}

.md-content .md-ul li[data-level="1"],
.md-content .md-ol li[data-level="1"] {
  margin-left: 20px;
}

.md-content .md-ul li[data-level="2"],
.md-content .md-ol li[data-level="2"] {
  margin-left: 40px;
}

.md-content .md-inline-code {
  background: #EEF0FF;
  color: var(--primary);
  padding: 2px 6px;
  border-radius: 4px;
  font-size: 13px;
  font-family: "SF Mono", "Fira Code", monospace;
}

.md-content .md-code-block {
  margin: 12px 0;
  border-radius: var(--radius-sm);
  overflow: hidden;
}

.md-content .md-code-block pre {
  background: #1E293B;
  color: #E2E8F0;
  padding: 16px;
  overflow-x: auto;
  font-size: 13px;
  line-height: 1.6;
  margin: 0;
}

.md-content .md-code-block pre code {
  background: none;
  color: inherit;
  padding: 0;
}

.md-content .md-table-wrapper {
  margin: 12px 0;
  overflow-x: auto;
  border-radius: var(--radius-sm);
  border: 1px solid var(--border);
}

.md-content .md-table {
  width: 100%;
  border-collapse: collapse;
  font-size: 13px;
}

.md-content .md-table th {
  padding: 10px 14px;
  text-align: left;
  background: var(--bg-light);
  font-weight: 600;
  color: var(--text-primary);
  border-bottom: 2px solid var(--border);
  white-space: nowrap;
}

.md-content .md-table td {
  padding: 10px 14px;
  border-bottom: 1px solid var(--border-light);
  color: var(--text-secondary);
}

.md-content .md-table tbody tr:last-child td {
  border-bottom: none;
}

.md-content .md-table tbody tr:hover {
  background: var(--bg-light);
}

/* ===== Footer ===== */
.footer {
  text-align: center;
  padding: 32px 24px;
  border-top: 1px solid var(--border-light);
  font-size: 13px;
  color: var(--text-muted);
}

/* ===== Mobile Menu ===== */
.mobile-menu-btn {
  display: none;
  background: none;
  border: none;
  cursor: pointer;
  padding: 8px;
  color: var(--text-primary);
}

.mobile-menu-btn svg {
  width: 24px;
  height: 24px;
}

/* ===== Responsive ===== */
@media (max-width: 768px) {
  .hero h1 {
    font-size: 32px;
  }

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

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

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

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

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

  .navbar-nav .nav-link-text {
    display: none;
  }

  .mobile-menu-btn {
    display: block;
  }

  .navbar-nav {
    display: none;
  }

  .navbar-nav.active {
    display: flex;
    flex-direction: column;
    position: absolute;
    top: 64px;
    left: 0;
    right: 0;
    background: var(--bg);
    border-bottom: 1px solid var(--border);
    padding: 16px;
    box-shadow: var(--shadow-lg);
  }

  .section-title {
    font-size: 26px;
  }

  .page-header h1 {
    font-size: 28px;
  }

  .result-content {
    padding: 16px;
  }

  .result-header {
    padding: 12px 16px;
  }
}

@media (max-width: 480px) {
  .hero h1 {
    font-size: 26px;
  }

  .hero h1 span {
    font-size: 22px;
  }

  .hero-actions {
    flex-direction: column;
  }

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

/* ===== Loading Animation ===== */
.loading-spinner {
  display: inline-block;
  width: 20px;
  height: 20px;
  border: 2px solid rgba(255,255,255,0.3);
  border-radius: 50%;
  border-top-color: #fff;
  animation: spin 0.8s ease-in-out infinite;
}

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

/* ===== Fade In Animation ===== */
.fade-in {
  opacity: 0;
  transform: translateY(20px);
  transition: opacity 0.6s ease, transform 0.6s ease;
}

.fade-in.visible {
  opacity: 1;
  transform: translateY(0);
}

/* ===== Tabs ===== */
.tabs {
  display: flex;
  border-bottom: 2px solid var(--border-light);
  margin-bottom: 24px;
  gap: 4px;
}

.tab-btn {
  padding: 10px 20px;
  font-size: 14px;
  font-weight: 600;
  color: var(--text-secondary);
  background: none;
  border: none;
  cursor: pointer;
  border-bottom: 2px solid transparent;
  margin-bottom: -2px;
  transition: var(--transition);
}

.tab-btn:hover {
  color: var(--primary);
}

.tab-btn.active {
  color: var(--primary);
  border-bottom-color: var(--primary);
}

.tab-content {
  display: none;
}

.tab-content.active {
  display: block;
}

/* ===== Toast ===== */
.toast {
  position: fixed;
  top: 80px;
  right: 24px;
  padding: 12px 20px;
  background: var(--text-primary);
  color: #fff;
  border-radius: var(--radius-sm);
  font-size: 14px;
  z-index: 9999;
  opacity: 0;
  transform: translateX(100%);
  transition: all 0.3s ease;
}

.toast.show {
  opacity: 1;
  transform: translateX(0);
}

/* ===== Copy Button ===== */
.copy-btn {
  position: absolute;
  top: 8px;
  right: 8px;
  padding: 4px 10px;
  font-size: 12px;
  background: rgba(255,255,255,0.1);
  color: #94A3B8;
  border: 1px solid rgba(255,255,255,0.1);
  border-radius: 4px;
  cursor: pointer;
  transition: var(--transition);
}

.copy-btn:hover {
  background: rgba(255,255,255,0.2);
  color: #fff;
}

.pre-wrapper {
  position: relative;
}

/* ===== Scrollbar for result area ===== */
.result-content::-webkit-scrollbar {
  width: 6px;
}

.result-content::-webkit-scrollbar-track {
  background: var(--bg-light);
  border-radius: 3px;
}

.result-content::-webkit-scrollbar-thumb {
  background: var(--border);
  border-radius: 3px;
}

.result-content::-webkit-scrollbar-thumb:hover {
  background: var(--text-muted);
}