:root {
  --bg: #f8f7f3;
  --surface: #ffffff;
  --surface-muted: #f4f2ed;
  --text: #1a1818;
  --muted: #656565;
  --accent: #1a8917;
  --border: #e6e3db;
  --divider-strong: #c29b56;
  --radius: 12px;
  --font-serif: 'Charter', 'Georgia', 'Times New Roman', serif;
  --font-sans: 'Helvetica Neue', Arial, sans-serif;
  --side-width: 260px;
  --main-pad: clamp(3rem, 5vw, 5.5rem);
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; }

body {
  margin: 0;
  font-family: var(--font-serif);
  background: #ffffff;
  color: var(--text);
  line-height: 1.75;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  font-size: 1.05rem;
}

a { color: inherit; text-decoration: none; }
a:hover { color: var(--accent); }
img { max-width: 100%; display: block; }

h1, h2, h3, h4, h5, h6 {
  font-family: var(--font-serif);
}

h1 { margin: 0 0 1.6rem; }
h2 { margin: 0 0 1.4rem; }
h3, h4, h5, h6 { margin: 0 0 1.1rem; }

/* ===== Header ===== */
.site-header {
  position: sticky;
  top: 0;
  z-index: 100;
  background: rgba(255, 255, 255, 0.96);
  backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--border);
  padding: 0;
}

.site-header .inner {
  width: min(1500px, 100% - 2rem);
  max-width: 1500px;
  margin: 0 auto;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
  padding: 0.75rem 0;
}

.logo {
  font-family: var(--font-sans);
  font-weight: 600;
  letter-spacing: 0.04em;
  text-transform: uppercase;
  color: var(--text);
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
}

.logo img {
  width: 28px;
  height: 28px;
  border-radius: 6px;
}

@media (min-width: 1200px) {
  .logo { min-width: var(--side-width); max-width: var(--side-width); }
  .site-header .inner {
    display: grid;
    grid-template-columns: var(--side-width) 1fr;
    align-items: center;
  }
}

.primary-nav .navbar-nav {
  flex-direction: row;
  align-items: center;
  gap: 0.6rem;
}

.primary-nav .nav-link {
  font-family: var(--font-sans);
  font-size: 0.95rem;
  padding: 0.35rem 0.6rem;
  color: var(--muted);
  border-radius: 8px;
}

.primary-nav .nav-link.active {
  color: var(--text);
  font-weight: 600;
}

.nav-toggle {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  background: transparent;
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 0.35rem 0.6rem;
}

/* ===== Layout ===== */
.layout {
  width: min(1500px, 100% - 2rem);
  max-width: 1500px;
  margin: 0 auto;
  flex: 1;
  padding: 2rem 0 4rem;
}

.main-content {
  padding: 0 var(--main-pad) 1rem;
  border-right: 1px solid var(--border);
}

.chapter-sidebar {
  align-self: start;
  position: sticky;
  top: 96px;
  background: transparent;
  font-family: var(--font-serif);
  max-height: calc(100vh - 130px);
  overflow-y: auto;
  padding-right: 1.5rem;
}

.chapter-sidebar::-webkit-scrollbar { width: 6px; }
.chapter-sidebar::-webkit-scrollbar-thumb { background: #c8c8c8; border-radius: 999px; }

.chapter-links,
.sub-chapter-links {
  list-style: none;
  margin: 0;
  padding: 0;
  display: flex;
  flex-direction: column;
  gap: 0.4rem;
}

.chapter-links a,
.chapter-links span {
  color: var(--muted);
  font-size: 0.95rem;
  display: block;
  padding: 0.25rem 0.3rem;
  border-radius: 8px;
}

.chapter-links > li { margin-bottom: 1rem; }
.chapter-links > li:last-child { margin-bottom: 0; }

.chapter-parent {
  font-family: var(--font-serif);
  font-weight: 400;
  color: var(--muted);
  margin-bottom: 0.6rem;
}

.chapter-links a:hover {
  background: var(--surface-muted);
  color: var(--text);
}

.chapter-links a.current {
  color: var(--accent);
  background: var(--surface-muted);
  box-shadow: inset 0 0 0 1px rgba(239, 227, 206, 0.8);
}

.sub-chapter-links {
  margin-left: 0.8rem;
  border-left: 1px solid var(--border);
  padding-left: 0.8rem;
}

/* ===== Content ===== */
.content-section + .content-section { margin-top: 3rem; }

.section-label {
  letter-spacing: 0.15em;
  text-transform: uppercase;
  font-size: 0.8rem;
  color: #a7a29a;
  font-weight: 600;
}

.section-title {
  margin: 0.2rem 0 1.6rem;
  font-size: 2.6rem;
  font-weight: 600;
}

.content-section h2 {
  font-size: 2rem;
  border-bottom: 1px solid var(--border);
  padding-bottom: 0.75rem;
  margin-bottom: 1.6rem;
}

.section-intro {
  color: var(--muted);
}

/* ===== Cards ===== */
.post-card-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: 1.25rem;
}

.post-card {
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 1.5rem;
  background: var(--surface);
  transition: border-color 0.2s, box-shadow 0.2s;
}

.post-card:hover {
  border-color: var(--accent);
  box-shadow: 0 4px 16px rgba(26, 137, 23, 0.08);
}

.post-card h3 {
  margin-top: 0;
  margin-bottom: 0.5rem;
  font-size: 1.15rem;
}

.post-card h3 a {
  color: var(--text);
  text-decoration: none;
}

.post-card h3 a:hover {
  color: var(--accent);
}

/* Category card variants */
.post-card--notes { border-left: 3px solid #4a90d9; }
.post-card--notes:hover { border-color: #4a90d9; box-shadow: 0 4px 16px rgba(74, 144, 217, 0.10); }
.post-card--notes .tag { background: #edf3fb; color: #3a7bc8; }

.post-card--qml { border-left: 3px solid #9b6dd7; }
.post-card--qml:hover { border-color: #9b6dd7; box-shadow: 0 4px 16px rgba(155, 109, 215, 0.10); }
.post-card--qml .tag { background: #f4edfb; color: #7c4fba; }

.post-card--dr-agent { border-left: 3px solid #d9864a; }
.post-card--dr-agent:hover { border-color: #d9864a; box-shadow: 0 4px 16px rgba(217, 134, 74, 0.10); }
.post-card--dr-agent .tag { background: #fdf3ed; color: #c07332; }

.post-card--systems { border-left: 3px solid #3aa8a0; }
.post-card--systems:hover { border-color: #3aa8a0; box-shadow: 0 4px 16px rgba(58, 168, 160, 0.10); }
.post-card--systems .tag { background: #e8f6f5; color: #2a7a74; }

.post-card p {
  color: var(--muted);
  font-size: 0.925rem;
  line-height: 1.6;
  margin-bottom: 0.75rem;
}

.post-date {
  color: #a7a29a;
  font-family: var(--font-sans);
  font-size: 0.85rem;
}

.tag-list {
  display: flex;
  flex-wrap: wrap;
  gap: 0.35rem;
  margin: 0.5rem 0;
}

.tag {
  padding: 0.25rem 0.6rem;
  border-radius: 999px;
  background: var(--surface-muted);
  font-family: var(--font-sans);
  font-size: 0.8rem;
  color: var(--muted);
}

/* ===== Code & Blockquote ===== */
pre, code {
  font-family: 'JetBrains Mono', 'Fira Code', 'SFMono-Regular', Menlo, Consolas, monospace;
  border-radius: 8px;
}

pre {
  padding: 1rem;
  overflow-x: auto;
  background: #2d2d2d !important;
  border: 1px solid #3a3a3a;
  margin: 1rem 0;
}

pre[class*="language-"] {
  margin: 1rem 0;
  padding: 1.2rem 1.4rem;
}

code {
  padding: 0.15rem 0.3rem;
  background: var(--surface-muted);
}

pre code {
  padding: 0;
  background: transparent;
  border: none;
  font-size: 0.85rem;
  line-height: 1.7;
  color: #f0f0f0;
}

code[class*="language-"] {
  text-shadow: none;
}

blockquote {
  margin: 1.5rem 0;
  padding: 1rem 1.2rem;
  border-left: 3px solid var(--border);
  background: var(--surface-muted);
  border-radius: 6px;
  font-style: italic;
}

/* ===== Page Nav ===== */
.page-nav {
  margin-top: 3rem;
  display: flex;
  justify-content: space-between;
  gap: 1rem;
  border-top: 1px solid var(--border);
  padding-top: 1.5rem;
}

.page-nav-btn {
  font-size: 0.95rem;
  padding: 0.65rem 1.2rem;
  border-radius: 999px;
  border: 1px solid var(--border);
  color: var(--text);
}

.page-nav-btn:hover {
  border-color: var(--accent);
  color: var(--accent);
}

/* ===== References ===== */
.ref-list {
  font-size: 0.9rem;
  line-height: 1.7;
  padding-left: 1.5rem;
}

.ref-list li {
  margin-bottom: 0.6rem;
  padding-left: 0.5rem;
}

.ref-list li::marker {
  font-weight: 600;
  color: var(--text);
}

/* ===== Footer ===== */
.footer {
  border-top: 1px solid var(--border);
  padding: 1.5rem;
  text-align: center;
  font-size: 0.9rem;
  color: var(--muted);
}

/* ===== Responsive ===== */
@media (max-width: 1100px) {
  .chapter-sidebar {
    position: static;
    max-height: none;
    padding: 0 var(--main-pad);
  }
  .main-content {
    border-right: none;
    padding: 0 var(--main-pad) 1rem;
  }
}

@media (max-width: 991.98px) {
  .site-header .inner {
    flex-wrap: wrap;
    width: min(1400px, 100% - 1.5rem);
    position: relative;
  }
  #mainNav {
    position: absolute;
    top: 100%;
    left: 0;
    right: 0;
    z-index: 10;
    background: #fff;
    padding: 0.75rem 1rem 1rem;
    border: 1px solid var(--border);
    border-radius: 12px;
    box-shadow: 0 12px 30px rgba(0, 0, 0, 0.1);
  }
  .primary-nav .navbar-nav {
    align-items: flex-start;
    flex-direction: column;
  }
  .primary-nav .nav-link { padding: 0.5rem 0; }
  .main-content {
    border-right: none;
    padding: 0 var(--main-pad) 1rem;
  }
}

@media (min-width: 1200px) {
  .chapter-sidebar {
    flex: 0 0 var(--side-width);
    max-width: var(--side-width);
    width: var(--side-width);
  }
  .main-content {
    flex: 1 1 0;
    width: auto;
    min-width: 0;
    max-width: calc(100% - var(--side-width));
  }
}

/* ===== Table ===== */
.table-scroll { overflow-x: auto; width: 100%; }

table {
  width: 100%;
  border-collapse: collapse;
  margin-top: 1rem;
}

table th, table td {
  border: 1px solid var(--border);
  padding: 0.65rem;
  text-align: left;
}

table th { background: var(--surface-muted); }