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

:root {
  --blue-50: #eff6ff;
  --blue-100: #dbeafe;
  --blue-200: #bfdbfe;
  --blue-400: #60a5fa;
  --blue-500: #3b82f6;
  --blue-600: #2563eb;
  --blue-700: #1d4ed8;
  --blue-800: #1e40af;
  --blue-900: #1e3a8a;

  --gray-50: #f9fafb;
  --gray-100: #f3f4f6;
  --gray-200: #e5e7eb;
  --gray-300: #d1d5db;
  --gray-400: #9ca3af;
  --gray-500: #6b7280;
  --gray-600: #4b5563;
  --gray-700: #374151;
  --gray-800: #1f2937;
  --gray-900: #111827;

  --nav-height: 56px;
  --sidebar-width: 260px;
  --content-max: 860px;
  --font-sans: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
  --font-mono: 'SF Mono', 'Fira Code', 'Fira Mono', Menlo, Consolas, monospace;
}

html { font-size: 16px; scroll-behavior: smooth; scroll-padding-top: calc(var(--nav-height) + 1rem); }

body {
  font-family: var(--font-sans);
  color: var(--gray-800);
  background: #fff;
  line-height: 1.7;
  -webkit-font-smoothing: antialiased;
}

/* === Top Navigation === */
.top-nav {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  height: var(--nav-height);
  background: #fff;
  border-bottom: 1px solid var(--gray-200);
  z-index: 100;
}

.top-nav-inner {
  max-width: 1400px;
  margin: 0 auto;
  height: 100%;
  display: flex;
  align-items: center;
  padding: 0 1.25rem;
  gap: 1.5rem;
}

.logo {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  text-decoration: none;
  color: var(--gray-900);
  font-weight: 700;
  font-size: 1.05rem;
  flex-shrink: 0;
}

.logo img { border-radius: 6px; }

.nav-links {
  display: flex;
  gap: 0.25rem;
  margin-left: 1rem;
}

.nav-links a {
  text-decoration: none;
  color: var(--gray-600);
  font-size: 0.875rem;
  font-weight: 500;
  padding: 0.375rem 0.75rem;
  border-radius: 6px;
  transition: color 0.15s, background 0.15s;
}

.nav-links a:hover {
  color: var(--blue-600);
  background: var(--blue-50);
}

.nav-actions { margin-left: auto; }

.github-link {
  display: flex;
  align-items: center;
  gap: 0.375rem;
  text-decoration: none;
  color: var(--gray-600);
  font-size: 0.875rem;
  font-weight: 500;
  padding: 0.375rem 0.75rem;
  border-radius: 6px;
  transition: color 0.15s, background 0.15s;
}

.github-link:hover {
  color: var(--gray-900);
  background: var(--gray-100);
}

.mobile-menu-btn {
  display: none;
  background: none;
  border: none;
  color: var(--gray-600);
  cursor: pointer;
  padding: 0.25rem;
  margin-left: auto;
}

/* === Layout === */
.layout {
  display: flex;
  margin-top: var(--nav-height);
  min-height: calc(100vh - var(--nav-height));
}

/* === Sidebar === */
.sidebar {
  position: fixed;
  top: var(--nav-height);
  left: 0;
  bottom: 0;
  width: var(--sidebar-width);
  overflow-y: auto;
  padding: 1.25rem 0;
  border-right: 1px solid var(--gray-200);
  background: var(--gray-50);
  z-index: 50;
}

.sidebar-nav { padding: 0 0.75rem; }

/* SUMMARY.md rendered structure: h1, h2 as section headings, ul/li/a as links */
.sidebar-nav > h1 { display: none; }

.sidebar-nav > h2 {
  font-size: 0.7rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--gray-400);
  padding: 0.75rem 0.75rem 0.25rem;
  margin: 0;
  border-top: 1px solid var(--gray-200);
}

.sidebar-nav > h2:first-of-type { border-top: none; }

.sidebar-nav > ul {
  list-style: none;
  padding: 0;
  margin: 0 0 0.25rem 0;
}

.sidebar-nav > ul > li { margin: 0; }

.sidebar-nav > ul > li > a {
  display: block;
  text-decoration: none;
  color: var(--gray-700);
  font-size: 0.85rem;
  padding: 0.3rem 0.75rem;
  border-radius: 6px;
  transition: color 0.15s, background 0.15s;
  line-height: 1.5;
}

.sidebar-nav > ul > li > a:hover {
  color: var(--blue-600);
  background: var(--blue-50);
}

.sidebar-nav > ul > li > a.active {
  color: var(--blue-700);
  background: var(--blue-100);
  font-weight: 600;
}

/* Nested lists (sub-items like diagram types) */
.sidebar-nav > ul > li > ul {
  list-style: none;
  padding: 0;
  margin: 0;
}

.sidebar-nav > ul > li > ul > li > a {
  display: block;
  text-decoration: none;
  color: var(--gray-600);
  font-size: 0.825rem;
  padding: 0.25rem 0.75rem 0.25rem 1.5rem;
  border-radius: 6px;
  transition: color 0.15s, background 0.15s;
  line-height: 1.5;
}

.sidebar-nav > ul > li > ul > li > a:hover {
  color: var(--blue-600);
  background: var(--blue-50);
}

.sidebar-nav > ul > li > ul > li > a.active {
  color: var(--blue-700);
  background: var(--blue-100);
  font-weight: 600;
}

/* === Content === */
.content {
  flex: 1;
  margin-left: var(--sidebar-width);
  min-width: 0;
}

.content-body {
  max-width: var(--content-max);
  margin: 0 auto;
  padding: 2.5rem 2rem 4rem;
}

/* === Typography === */
.content-body h1 {
  font-size: 2rem;
  font-weight: 700;
  color: var(--gray-900);
  margin-bottom: 0.75rem;
  line-height: 1.3;
  padding-bottom: 0.5rem;
  border-bottom: 2px solid var(--blue-500);
}

.content-body h2 {
  font-size: 1.45rem;
  font-weight: 700;
  color: var(--gray-900);
  margin-top: 2.5rem;
  margin-bottom: 0.625rem;
  padding-bottom: 0.375rem;
  border-bottom: 1px solid var(--gray-200);
}

.content-body h3 {
  font-size: 1.2rem;
  font-weight: 600;
  color: var(--gray-800);
  margin-top: 2rem;
  margin-bottom: 0.5rem;
}

.content-body h4 {
  font-size: 1.05rem;
  font-weight: 600;
  color: var(--gray-700);
  margin-top: 1.5rem;
  margin-bottom: 0.375rem;
}

.content-body p {
  margin-bottom: 1rem;
}

.content-body a {
  color: var(--blue-600);
  text-decoration: none;
  font-weight: 500;
}

.content-body a:hover { text-decoration: underline; }

.content-body strong { font-weight: 600; color: var(--gray-900); }

.content-body hr {
  border: none;
  border-top: 1px solid var(--gray-200);
  margin: 2rem 0;
}

/* Lists */
.content-body ul, .content-body ol {
  padding-left: 1.5rem;
  margin-bottom: 1rem;
}

.content-body li { margin-bottom: 0.375rem; }
.content-body li > ul, .content-body li > ol { margin-top: 0.375rem; margin-bottom: 0; }

/* Code */
.content-body code {
  font-family: var(--font-mono);
  font-size: 0.875em;
  background: var(--blue-50);
  color: var(--blue-800);
  padding: 0.15em 0.4em;
  border-radius: 4px;
}

.content-body pre {
  background: var(--gray-900);
  color: var(--gray-100);
  border-radius: 8px;
  padding: 1rem 1.25rem;
  overflow-x: auto;
  margin-bottom: 1.25rem;
  line-height: 1.6;
  font-size: 0.875rem;
}

.content-body pre code {
  background: none;
  color: inherit;
  padding: 0;
  font-size: inherit;
}

/* Tables */
.content-body table {
  width: 100%;
  border-collapse: collapse;
  margin-bottom: 1.25rem;
  font-size: 0.9rem;
}

.content-body th {
  background: var(--blue-600);
  color: #fff;
  font-weight: 600;
  text-align: left;
  padding: 0.625rem 0.875rem;
}

.content-body th:first-child { border-radius: 6px 0 0 0; }
.content-body th:last-child { border-radius: 0 6px 0 0; }

.content-body td {
  padding: 0.5rem 0.875rem;
  border-bottom: 1px solid var(--gray-200);
}

.content-body tr:hover td { background: var(--blue-50); }

/* Blockquote */
.content-body blockquote {
  border-left: 3px solid var(--blue-500);
  background: var(--blue-50);
  padding: 0.75rem 1rem;
  margin: 0 0 1rem 0;
  border-radius: 0 6px 6px 0;
  color: var(--gray-700);
}

.content-body blockquote p:last-child { margin-bottom: 0; }

/* Images */
.content-body img {
  max-width: 100%;
  height: auto;
  border-radius: 8px;
}

/* === Footer === */
.site-footer {
  background: var(--gray-900);
  color: var(--gray-300);
  margin-left: var(--sidebar-width);
}

.footer-inner {
  max-width: var(--content-max);
  margin: 0 auto;
  padding: 3rem 2rem 2rem;
}

.footer-grid {
  display: grid;
  grid-template-columns: 1.5fr 1fr 1fr 1fr;
  gap: 2rem;
  margin-bottom: 2rem;
}

.footer-logo {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  color: #fff;
  font-weight: 700;
  font-size: 1rem;
  margin-bottom: 0.5rem;
}

.footer-logo img { border-radius: 5px; }

.footer-desc {
  font-size: 0.85rem;
  color: var(--gray-400);
  line-height: 1.5;
}

.footer-col {
  display: flex;
  flex-direction: column;
  gap: 0.375rem;
}

.footer-col-title {
  font-weight: 600;
  color: #fff;
  font-size: 0.85rem;
  margin-bottom: 0.375rem;
  text-transform: uppercase;
  letter-spacing: 0.04em;
}

.footer-col a {
  color: var(--gray-400);
  text-decoration: none;
  font-size: 0.85rem;
  transition: color 0.15s;
}

.footer-col a:hover { color: var(--blue-400); }

.footer-bottom {
  border-top: 1px solid var(--gray-700);
  padding-top: 1.25rem;
  font-size: 0.8rem;
  color: var(--gray-500);
}

/* === Sidebar Overlay (mobile) === */
.sidebar-overlay {
  display: none;
  position: fixed;
  inset: 0;
  background: rgba(0,0,0,0.4);
  z-index: 40;
}

.sidebar-overlay.open { display: block; }

/* === Responsive === */
@media (max-width: 900px) {
  .nav-links { display: none; }
  .github-link span { display: none; }
  .mobile-menu-btn { display: block; }

  .sidebar {
    transform: translateX(-100%);
    transition: transform 0.25s ease;
    background: #fff;
  }

  .sidebar.open { transform: translateX(0); }

  .content { margin-left: 0; }
  .site-footer { margin-left: 0; }

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

  .content-body {
    padding: 1.5rem 1.25rem 3rem;
  }
}

@media (max-width: 600px) {
  .footer-grid {
    grid-template-columns: 1fr;
  }

  .content-body h1 { font-size: 1.6rem; }
  .content-body h2 { font-size: 1.25rem; }
}