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

:root {
  --color-bg: #ffffff;
  --color-surface: #f8f9fa;
  --color-border: #e1e4e8;
  --color-primary: #0969da;
  --color-primary-dark: #0550ae;
  --color-text: #24292f;
  --color-text-muted: #57606a;
  --color-code-bg: #f6f8fa;
  --color-accent: #2da44e;
  --font-sans: -apple-system, BlinkMacSystemFont, "Segoe UI", Helvetica, Arial, sans-serif;
  --font-mono: ui-monospace, SFMono-Regular, SF Mono, Menlo, Consolas, "Liberation Mono", monospace;
  --max-width: 1200px;
  --radius: 6px;
}

body {
  font-family: var(--font-sans);
  font-size: 16px;
  line-height: 1.6;
  color: var(--color-text);
  background: var(--color-bg);
}

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

a:hover {
  text-decoration: underline;
}

/* External link icon */

a[target="_blank"]:not(.btn):not([style*="text-decoration:none"])::after {
  content: '';
  display: inline-block;
  width: 10px;
  height: 10px;
  margin-left: 3px;
  vertical-align: middle;
  background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='10' height='10' viewBox='0 0 16 16'%3E%3Cpath fill='%2357606a' d='M3.75 2h3.5a.75.75 0 0 1 0 1.5h-3.5a.25.25 0 0 0-.25.25v8.5c0 .138.112.25.25.25h8.5a.25.25 0 0 0 .25-.25v-3.5a.75.75 0 0 1 1.5 0v3.5A1.75 1.75 0 0 1 12.25 14h-8.5A1.75 1.75 0 0 1 2 12.25v-8.5C2 2.784 2.784 2 3.75 2Zm6.854-1h4.146a.25.25 0 0 1 .25.25v4.146a.25.25 0 0 1-.427.177L13.03 4.03 9.28 7.78a.751.751 0 0 1-1.042-.018.751.751 0 0 1-.018-1.042l3.75-3.75-1.543-1.543A.25.25 0 0 1 10.604 1Z'/%3E%3C/svg%3E");
  background-size: contain;
  background-repeat: no-repeat;
  background-position: center;
  opacity: 0.6;
  flex-shrink: 0;
}

/* Layout */
.container {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 24px;
}

/* Header / Nav */
.site-header {
  border-bottom: 1px solid var(--color-border);
  padding: 14px 0;
  background: var(--color-bg);
  position: sticky;
  top: 0;
  z-index: 100;
}

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

.site-logo {
  font-size: 18px;
  font-weight: 700;
  color: var(--color-text);
  display: flex;
  align-items: center;
  gap: 8px;
}

.site-logo .ext {
  color: var(--color-primary);
}

.site-nav {
  display: flex;
  gap: 24px;
  list-style: none;
}

.site-nav a {
  color: var(--color-text-muted);
  font-size: 14px;
  font-weight: 500;
}

.site-nav a:hover {
  color: var(--color-text);
  text-decoration: none;
}

/* Hero */
.hero {
  padding: 80px 0 64px;
  text-align: center;
  background: linear-gradient(180deg, #f6f8fa 0%, #ffffff 100%);
  border-bottom: 1px solid var(--color-border);
}

.hero-badge {
  display: inline-block;
  background: #ddf4ff;
  color: #0550ae;
  border: 1px solid #b6e3ff;
  border-radius: 2em;
  font-size: 12px;
  font-weight: 600;
  padding: 4px 12px;
  margin-bottom: 20px;
  letter-spacing: 0.03em;
  text-transform: uppercase;
}

.hero h1 {
  font-size: 48px;
  font-weight: 800;
  line-height: 1.15;
  color: var(--color-text);
  margin-bottom: 16px;
}

.hero h1 .ext {
  color: var(--color-primary);
}

.hero-subtitle {
  font-size: 20px;
  color: var(--color-text-muted);
  max-width: 600px;
  margin: 0 auto 36px;
}

.hero-actions {
  display: flex;
  gap: 12px;
  justify-content: center;
  flex-wrap: wrap;
}

.btn {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 10px 20px;
  border-radius: var(--radius);
  font-size: 14px;
  font-weight: 600;
  cursor: pointer;
  transition: background 0.15s, border-color 0.15s;
  text-decoration: none;
}

.btn-primary {
  background: var(--color-primary);
  color: #ffffff;
  border: 1px solid var(--color-primary);
}

.btn-primary:hover {
  background: var(--color-primary-dark);
  border-color: var(--color-primary-dark);
  text-decoration: none;
  color: #ffffff;
}

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

.btn-secondary:hover {
  background: var(--color-surface);
  text-decoration: none;
}

/* Sections */
section {
  padding: 64px 0;
}

section + section {
  border-top: 1px solid var(--color-border);
}

.section-label {
  font-size: 12px;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--color-primary);
  margin-bottom: 8px;
}

h2 {
  font-size: 32px;
  font-weight: 700;
  line-height: 1.25;
  margin-bottom: 12px;
}

h3 {
  font-size: 20px;
  font-weight: 600;
  margin-bottom: 8px;
}

.section-intro {
  font-size: 18px;
  color: var(--color-text-muted);
  max-width: 680px;
  margin-bottom: 40px;
}

/* Feature grid */
.features-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(260px, 1fr));
  gap: 24px;
  margin-top: 40px;
}

.feature-card {
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  padding: 24px;
}

.feature-icon {
  font-size: 28px;
  margin-bottom: 12px;
}

.feature-card h3 {
  font-size: 16px;
  margin-bottom: 6px;
}

.feature-card p {
  font-size: 14px;
  color: var(--color-text-muted);
  line-height: 1.5;
}

/* Code block */
.code-block {
  background: var(--color-code-bg);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  overflow: hidden;
  margin: 24px 0;
}

.code-block-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 8px 16px;
  background: var(--color-border);
  font-size: 12px;
  font-weight: 600;
  color: var(--color-text-muted);
}

.code-block pre {
  padding: 20px;
  overflow-x: auto;
  margin: 0;
}

.code-block code {
  font-family: var(--font-mono);
  font-size: 13px;
  line-height: 1.6;
  color: var(--color-text);
}

/* Structure diagram */
.structure-diagram {
  background: var(--color-code-bg);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  padding: 24px 32px;
  font-family: var(--font-mono);
  font-size: 13px;
  line-height: 1.8;
  margin: 24px 0;
}

.structure-diagram .tree-root {
  font-weight: 700;
  color: var(--color-primary);
}

.structure-diagram .tree-dir {
  color: var(--color-accent);
  font-weight: 600;
}

.structure-diagram .tree-file {
  color: var(--color-text);
}

.structure-diagram .tree-comment {
  color: var(--color-text-muted);
}

/* Two-column layout */
.two-col {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 40px;
  align-items: start;
}

@media (max-width: 700px) {
  .two-col {
    grid-template-columns: 1fr;
  }
}

/* Steps list */
.steps {
  counter-reset: steps;
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: 20px;
}

.steps li {
  counter-increment: steps;
  display: flex;
  gap: 16px;
}

.steps li::before {
  content: counter(steps);
  flex-shrink: 0;
  width: 32px;
  height: 32px;
  background: var(--color-primary);
  color: #fff;
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 14px;
  font-weight: 700;
  margin-top: 2px;
}

.steps li p {
  font-size: 15px;
}

.steps li strong {
  display: block;
  margin-bottom: 2px;
}

/* Table */
.spec-table {
  width: 100%;
  border-collapse: collapse;
  font-size: 14px;
  margin: 24px 0;
}

.spec-table th {
  text-align: left;
  padding: 10px 14px;
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  font-weight: 600;
  color: var(--color-text-muted);
  font-size: 12px;
  text-transform: uppercase;
  letter-spacing: 0.04em;
}

.spec-table td {
  padding: 10px 14px;
  border: 1px solid var(--color-border);
  vertical-align: top;
  line-height: 1.5;
}

.spec-table tr:nth-child(even) td {
  background: var(--color-surface);
}

code {
  font-family: var(--font-mono);
  font-size: 0.875em;
  background: var(--color-code-bg);
  border: 1px solid var(--color-border);
  border-radius: 4px;
  padding: 1px 5px;
}

/* Copy button */
.copy-btn {
  display: inline-flex;
  align-items: center;
  gap: 4px;
  padding: 2px 8px;
  background: transparent;
  border: 1px solid rgba(255,255,255,0.3);
  border-radius: 4px;
  color: var(--color-text-muted);
  font-size: 11px;
  font-family: var(--font-sans);
  font-weight: 500;
  cursor: pointer;
  transition: background 0.15s, color 0.15s, border-color 0.15s;
  white-space: nowrap;
}

.copy-btn:hover {
  background: var(--color-border);
  color: var(--color-text);
  border-color: var(--color-border);
}

.copy-btn.copied {
  color: var(--color-accent);
  border-color: var(--color-accent);
}

/* CTA Banner */
.cta-banner {
  background: var(--color-primary);
  color: #ffffff;
  border-radius: var(--radius);
  padding: 48px 40px;
  text-align: center;
}

.cta-banner h2 {
  color: #ffffff;
  margin-bottom: 12px;
}

.cta-banner p {
  color: rgba(255,255,255,0.85);
  font-size: 16px;
  margin-bottom: 28px;
  max-width: 480px;
  margin-left: auto;
  margin-right: auto;
}

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

.btn-white:hover {
  background: #f0f6fc;
  border-color: #f0f6fc;
  text-decoration: none;
  color: var(--color-primary);
}

.btn-outline-white {
  background: transparent;
  color: #ffffff;
  border: 1px solid rgba(255,255,255,0.5);
}

.btn-outline-white:hover {
  background: rgba(255,255,255,0.1);
  border-color: #ffffff;
  text-decoration: none;
  color: #ffffff;
}

/* Footer */
.site-footer {
  border-top: 1px solid var(--color-border);
  padding: 32px 0;
  font-size: 14px;
  color: var(--color-text-muted);
}

.site-footer .container {
  display: flex;
  align-items: center;
  justify-content: space-between;
  flex-wrap: wrap;
  gap: 16px;
}

.site-footer a {
  color: var(--color-text-muted);
}

.site-footer a:hover {
  color: var(--color-text);
}

.footer-links {
  display: flex;
  gap: 20px;
  list-style: none;
}

/* Spec page */
.spec-nav {
  position: sticky;
  top: 61px;
  max-height: calc(100vh - 80px);
  overflow-y: auto;
  padding-right: 8px;
}

.spec-nav ul {
  list-style: none;
  border-left: 2px solid var(--color-border);
  padding-left: 16px;
}

.spec-nav ul ul {
  margin-top: 4px;
  margin-left: 12px;
  border-left-width: 1px;
}

.spec-nav a {
  display: block;
  font-size: 13px;
  color: var(--color-text-muted);
  padding: 3px 0;
}

.spec-nav a:hover {
  color: var(--color-text);
  text-decoration: none;
}

.spec-nav .nav-section {
  font-size: 11px;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--color-text-muted);
  margin-top: 16px;
  margin-bottom: 4px;
}

.spec-layout {
  display: grid;
  grid-template-columns: 220px 1fr;
  gap: 48px;
  padding-top: 40px;
}

@media (max-width: 800px) {
  .spec-layout {
    grid-template-columns: 1fr;
  }
  .spec-nav {
    display: none;
  }
}

.spec-content h2 {
  font-size: 26px;
  margin-top: 48px;
  margin-bottom: 12px;
  padding-bottom: 8px;
  border-bottom: 1px solid var(--color-border);
}

.spec-content h2:first-child {
  margin-top: 0;
}

.spec-content h3 {
  font-size: 18px;
  margin-top: 28px;
  margin-bottom: 8px;
}

.spec-content p {
  margin-bottom: 16px;
  font-size: 15px;
  line-height: 1.7;
}

.spec-content ul, .spec-content ol {
  padding-left: 24px;
  margin-bottom: 16px;
}

.spec-content li {
  font-size: 15px;
  line-height: 1.7;
  margin-bottom: 4px;
}

.spec-content .note {
  background: #ddf4ff;
  border-left: 4px solid #0969da;
  border-radius: 0 var(--radius) var(--radius) 0;
  padding: 12px 16px;
  font-size: 14px;
  margin: 20px 0;
}

.spec-content .warning {
  background: #fff8c5;
  border-left: 4px solid #d29922;
  border-radius: 0 var(--radius) var(--radius) 0;
  padding: 12px 16px;
  font-size: 14px;
  margin: 20px 0;
}

/* Responsive */
@media (max-width: 600px) {
  .hero h1 {
    font-size: 34px;
  }

  .hero-subtitle {
    font-size: 16px;
  }

  h2 {
    font-size: 24px;
  }

  .site-header .container {
    flex-wrap: wrap;
    gap: 8px;
  }

  .site-nav {
    display: flex;
    flex-wrap: wrap;
    gap: 8px 16px;
    font-size: 13px;
  }

  .features-grid[style*="repeat(4"] {
    grid-template-columns: repeat(2, 1fr) !important;
  }
}

@media (max-width: 400px) {
  .features-grid[style*="repeat(4"] {
    grid-template-columns: 1fr !important;
  }
}