/* Programming Neam — Interactive Book Styles */
:root {
  --red: #BE0027;
  --blue: #0060B6;
  --dark: #333333;
  --bg: #ffffff;
  --bg-secondary: #f6f8fa;
  --text: #24292f;
  --text-secondary: #57606a;
  --border: #d0d7de;
  --sidebar-bg: #f6f8fa;
  --sidebar-width: 280px;
  --topbar-height: 56px;
  --content-max: 800px;
  --code-bg: #f6f8fa;
  --code-border: #d0d7de;
  --shadow: 0 1px 3px rgba(0,0,0,0.12);
  --shadow-lg: 0 8px 24px rgba(0,0,0,0.12);
  --radius: 8px;
  --transition: 0.2s ease;
}

[data-theme="dark"] {
  --bg: #0d1117;
  --bg-secondary: #161b22;
  --text: #c9d1d9;
  --text-secondary: #8b949e;
  --border: #30363d;
  --sidebar-bg: #161b22;
  --code-bg: #161b22;
  --code-border: #30363d;
  --shadow: 0 1px 3px rgba(0,0,0,0.3);
  --shadow-lg: 0 8px 24px rgba(0,0,0,0.4);
}

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

html { scroll-behavior: smooth; scroll-padding-top: calc(var(--topbar-height) + 16px); }

body {
  font-family: Georgia, 'Times New Roman', serif;
  font-size: 17px;
  line-height: 1.7;
  color: var(--text);
  background: var(--bg);
  transition: background var(--transition), color var(--transition);
  -webkit-font-smoothing: antialiased;
}

/* ── Topbar ── */
.topbar {
  position: fixed;
  top: 0; left: 0; right: 0;
  height: var(--topbar-height);
  background: var(--bg);
  border-bottom: 1px solid var(--border);
  display: flex;
  align-items: center;
  padding: 0 20px;
  z-index: 100;
  transition: background var(--transition), border-color var(--transition);
}
.topbar-left { display: flex; align-items: center; gap: 12px; }
.hamburger {
  display: none;
  background: none;
  border: none;
  cursor: pointer;
  padding: 4px;
  color: var(--text);
  font-size: 22px;
  line-height: 1;
}
.topbar-title {
  font-family: Inter, Arial, Helvetica, sans-serif;
  font-size: 16px;
  font-weight: 700;
  color: var(--red);
  text-decoration: none;
}
.topbar-title:hover { opacity: 0.8; }
.topbar-right { margin-left: auto; display: flex; align-items: center; gap: 8px; }
.topbar-btn {
  background: none;
  border: 1px solid var(--border);
  border-radius: 6px;
  padding: 6px 12px;
  cursor: pointer;
  color: var(--text-secondary);
  font-size: 13px;
  font-family: Inter, Arial, sans-serif;
  display: flex; align-items: center; gap: 6px;
  transition: all var(--transition);
}
.topbar-btn:hover { border-color: var(--blue); color: var(--blue); }
.search-btn kbd {
  background: var(--bg-secondary);
  border: 1px solid var(--border);
  border-radius: 4px;
  padding: 1px 5px;
  font-size: 11px;
  font-family: Inter, Arial, sans-serif;
}

/* ── Progress Bar ── */
.progress-bar {
  position: fixed;
  top: var(--topbar-height);
  left: 0; right: 0;
  height: 3px;
  background: var(--border);
  z-index: 99;
}
.progress-fill {
  height: 100%;
  background: linear-gradient(90deg, var(--blue), var(--red));
  width: 0%;
  transition: width 0.1s linear;
}

/* ── Sidebar ── */
.sidebar {
  position: fixed;
  top: var(--topbar-height);
  left: 0;
  bottom: 0;
  width: var(--sidebar-width);
  background: var(--sidebar-bg);
  border-right: 1px solid var(--border);
  overflow-y: auto;
  padding: 16px 0;
  z-index: 90;
  transition: background var(--transition), transform 0.3s ease, border-color var(--transition);
}
.sidebar-overlay {
  display: none;
  position: fixed;
  inset: 0;
  background: rgba(0,0,0,0.5);
  z-index: 89;
}
.sidebar-part {
  padding: 0 16px;
  margin-bottom: 4px;
}
.sidebar-part-title {
  font-family: Inter, Arial, sans-serif;
  font-size: 11px;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--text-secondary);
  padding: 8px 0 4px;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: space-between;
  user-select: none;
}
.sidebar-part-title::after {
  content: '\25B6';
  font-size: 8px;
  transition: transform 0.2s;
}
.sidebar-part-title.open::after {
  transform: rotate(90deg);
}
.sidebar-chapters {
  overflow: hidden;
  max-height: 0;
  transition: max-height 0.3s ease;
}
.sidebar-chapters.open {
  max-height: 2000px;
}
.sidebar-link {
  display: block;
  padding: 5px 12px;
  font-family: Inter, Arial, sans-serif;
  font-size: 13px;
  color: var(--text-secondary);
  text-decoration: none;
  border-radius: 4px;
  transition: all var(--transition);
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}
.sidebar-link:hover {
  background: var(--bg);
  color: var(--text);
}
.sidebar-link.active {
  background: var(--blue);
  color: #fff;
  font-weight: 600;
}
.sidebar-link .visited-dot {
  display: inline-block;
  width: 6px; height: 6px;
  border-radius: 50%;
  background: var(--blue);
  margin-right: 6px;
  vertical-align: middle;
}

/* ── Main Content ── */
.main {
  margin-left: var(--sidebar-width);
  margin-top: var(--topbar-height);
  min-height: calc(100vh - var(--topbar-height));
}
.content {
  max-width: var(--content-max);
  margin: 0 auto;
  padding: 40px 32px 80px;
}

/* ── Typography ── */
h1, h2, h3, h4, h5, h6 {
  font-family: Inter, Arial, Helvetica, sans-serif;
  color: var(--text);
  margin-top: 2em;
  margin-bottom: 0.5em;
  line-height: 1.3;
  scroll-margin-top: calc(var(--topbar-height) + 20px);
}
h1 { font-size: 2em; margin-top: 0; padding-bottom: 0.3em; border-bottom: 2px solid var(--red); }
h2 { font-size: 1.5em; padding-bottom: 0.2em; border-bottom: 1px solid var(--border); }
h3 { font-size: 1.25em; }
h4 { font-size: 1.1em; }
.heading-anchor {
  opacity: 0;
  margin-left: 8px;
  color: var(--text-secondary);
  text-decoration: none;
  font-size: 0.8em;
  transition: opacity var(--transition);
}
h1:hover .heading-anchor,
h2:hover .heading-anchor,
h3:hover .heading-anchor,
h4:hover .heading-anchor { opacity: 1; }

p { margin-bottom: 1em; }
a { color: var(--blue); text-decoration: none; }
a:hover { text-decoration: underline; }
blockquote {
  border-left: 4px solid var(--border);
  margin: 1em 0;
  padding: 0.5em 1em;
  color: var(--text-secondary);
  background: var(--bg-secondary);
  border-radius: 0 var(--radius) var(--radius) 0;
}
hr {
  border: none;
  border-top: 1px solid var(--border);
  margin: 2em 0;
}
ul, ol {
  margin: 0.5em 0 1em 1.5em;
}
li { margin-bottom: 0.3em; }
strong { color: var(--text); }
img { max-width: 100%; border-radius: var(--radius); }

/* ── Code Blocks ── */
code {
  font-family: 'JetBrains Mono', 'Fira Code', 'Courier New', Courier, monospace;
  font-size: 0.88em;
  background: var(--code-bg);
  border: 1px solid var(--code-border);
  border-radius: 4px;
  padding: 2px 6px;
}
pre {
  background: var(--code-bg);
  border: 1px solid var(--code-border);
  border-radius: var(--radius);
  padding: 16px 20px;
  overflow-x: auto;
  margin: 1em 0;
  position: relative;
  line-height: 1.5;
}
pre code {
  background: none;
  border: none;
  padding: 0;
  font-size: 0.85em;
}
.code-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  background: var(--bg-secondary);
  border: 1px solid var(--code-border);
  border-bottom: none;
  border-radius: var(--radius) var(--radius) 0 0;
  padding: 6px 12px;
  font-family: Inter, Arial, sans-serif;
  font-size: 12px;
  color: var(--text-secondary);
}
.code-header + pre {
  border-top-left-radius: 0;
  border-top-right-radius: 0;
  margin-top: 0;
}
.copy-btn {
  background: none;
  border: 1px solid var(--border);
  border-radius: 4px;
  padding: 3px 8px;
  cursor: pointer;
  font-size: 12px;
  color: var(--text-secondary);
  font-family: Inter, Arial, sans-serif;
  transition: all var(--transition);
}
.copy-btn:hover { border-color: var(--blue); color: var(--blue); }
.copy-btn.copied { border-color: #1a7f37; color: #1a7f37; }

/* Syntax highlighting */
.kw { color: #cf222e; font-weight: 600; }
[data-theme="dark"] .kw { color: #ff7b72; }
.str { color: #0a3069; }
[data-theme="dark"] .str { color: #a5d6ff; }
.num { color: #0550ae; }
[data-theme="dark"] .num { color: #79c0ff; }
.cm { color: #6e7781; font-style: italic; }
[data-theme="dark"] .cm { color: #8b949e; }
.fn { color: #8250df; }
[data-theme="dark"] .fn { color: #d2a8ff; }
.op { color: #cf222e; }
[data-theme="dark"] .op { color: #ff7b72; }
.type { color: #0550ae; font-weight: 600; }
[data-theme="dark"] .type { color: #79c0ff; }

/* ── Callouts ── */
.callout {
  border-left: 4px solid var(--border);
  border-radius: 0 var(--radius) var(--radius) 0;
  padding: 16px 20px;
  margin: 1.5em 0;
  line-height: 1.6;
}
.callout-title {
  font-family: Inter, Arial, sans-serif;
  font-weight: 700;
  font-size: 0.95em;
  margin-bottom: 8px;
  display: flex;
  align-items: center;
  gap: 8px;
}
.callout-title .callout-icon { font-size: 1.1em; }
.callout p { margin-bottom: 0.5em; }
.callout p:last-child { margin-bottom: 0; }

.callout-note {
  border-left-color: #0060B6;
  background: #e8f0fe;
}
.callout-note .callout-title {
  color: #0060B6;
}
[data-theme="dark"] .callout-note {
  background: #1a2d4a;
  border-left-color: #0060B6;
}

.callout-tip {
  border-left-color: #1a7f37;
  background: #dafbe1;
}
.callout-tip .callout-title {
  color: #1a7f37;
}
[data-theme="dark"] .callout-tip {
  background: #1a3a2a;
  border-left-color: #1a7f37;
}

.callout-warning {
  border-left-color: #9a6700;
  background: #fff8c5;
}
.callout-warning .callout-title {
  color: #9a6700;
}
[data-theme="dark"] .callout-warning {
  background: #3a3520;
  border-left-color: #9a6700;
}

.callout-common-mistake {
  border-left-color: #cf222e;
  background: #ffebe9;
}
.callout-common-mistake .callout-title {
  color: #cf222e;
}
[data-theme="dark"] .callout-common-mistake {
  background: #3a1a1a;
  border-left-color: #cf222e;
}

.callout-try-it-yourself {
  border-left-color: #8250df;
  background: #f3e8ff;
}
.callout-try-it-yourself .callout-title {
  color: #8250df;
}
[data-theme="dark"] .callout-try-it-yourself {
  background: #2d1a4a;
  border-left-color: #8250df;
}

.callout-why-this-matters {
  border-left-color: #3730a3;
  background: #e8e7fe;
}
.callout-why-this-matters .callout-title {
  color: #3730a3;
}
[data-theme="dark"] .callout-why-this-matters {
  background: #1a1a4a;
  border-left-color: #3730a3;
}

.callout-real-world-analogy {
  border-left-color: #7c4a1a;
  background: #fef3e2;
}
.callout-real-world-analogy .callout-title {
  color: #7c4a1a;
}
[data-theme="dark"] .callout-real-world-analogy {
  background: #3a2a1a;
  border-left-color: #7c4a1a;
}

.callout-important {
  border-left-color: #9a6700;
  background: #fff8c5;
}
.callout-important .callout-title {
  color: #9a6700;
}
[data-theme="dark"] .callout-important {
  background: #3a3520;
  border-left-color: #9a6700;
}

.callout-key-point {
  border-left-color: #0060B6;
  background: #e8f0fe;
}
.callout-key-point .callout-title {
  color: #0060B6;
}
[data-theme="dark"] .callout-key-point {
  background: #1a2d4a;
  border-left-color: #0060B6;
}

.callout-key-insight {
  border-left-color: #0060B6;
  background: #e8f0fe;
}
.callout-key-insight .callout-title {
  color: #0060B6;
}
[data-theme="dark"] .callout-key-insight {
  background: #1a2d4a;
  border-left-color: #0060B6;
}

.callout-key-design-decision {
  border-left-color: #0060B6;
  background: #e8f0fe;
}
.callout-key-design-decision .callout-title {
  color: #0060B6;
}
[data-theme="dark"] .callout-key-design-decision {
  background: #1a2d4a;
  border-left-color: #0060B6;
}

.callout-design-choice {
  border-left-color: #0060B6;
  background: #e8f0fe;
}
.callout-design-choice .callout-title {
  color: #0060B6;
}
[data-theme="dark"] .callout-design-choice {
  background: #1a2d4a;
  border-left-color: #0060B6;
}

.callout-pro-tip {
  border-left-color: #1a7f37;
  background: #dafbe1;
}
.callout-pro-tip .callout-title {
  color: #1a7f37;
}
[data-theme="dark"] .callout-pro-tip {
  background: #1a3a2a;
  border-left-color: #1a7f37;
}

.callout-edge-case {
  border-left-color: #9a6700;
  background: #fff8c5;
}
.callout-edge-case .callout-title {
  color: #9a6700;
}
[data-theme="dark"] .callout-edge-case {
  background: #3a3520;
  border-left-color: #9a6700;
}

.callout-recommendation {
  border-left-color: #1a7f37;
  background: #dafbe1;
}
.callout-recommendation .callout-title {
  color: #1a7f37;
}
[data-theme="dark"] .callout-recommendation {
  background: #1a3a2a;
  border-left-color: #1a7f37;
}

.callout-looking-ahead {
  border-left-color: #3730a3;
  background: #e8e7fe;
}
.callout-looking-ahead .callout-title {
  color: #3730a3;
}
[data-theme="dark"] .callout-looking-ahead {
  background: #1a1a4a;
  border-left-color: #3730a3;
}


/* ── Diagrams (monospace fallback) ── */
.diagram {
  background: linear-gradient(135deg, var(--bg-secondary), var(--bg));
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 24px;
  margin: 1.5em 0;
  overflow-x: auto;
  text-align: center;
}
.diagram pre {
  background: none;
  border: none;
  padding: 0;
  margin: 0;
  display: inline-block;
  text-align: left;
  font-size: 0.82em;
  line-height: 1.4;
}
.diagram pre code {
  background: none;
  border: none;
}
[data-theme="dark"] .diagram {
  background: linear-gradient(135deg, #1a2332, var(--bg-secondary));
}

/* ── Box Diagrams ── */
.box-diagram {
  background: linear-gradient(145deg, #f8fafc, #eef2ff);
  border: 1px solid #c7d2de;
  border-radius: 12px;
  padding: 20px;
  margin: 1.5em 0;
  box-shadow: 0 4px 16px rgba(0,0,0,0.06);
  overflow-x: auto;
}
[data-theme="dark"] .box-diagram {
  background: linear-gradient(145deg, #0f172a, #1e1b4b);
  border-color: #312e81;
  box-shadow: 0 4px 16px rgba(0,0,0,0.3);
}
.bd-title {
  font-family: Inter, Arial, sans-serif;
  font-weight: 700;
  font-size: 0.85em;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--text-secondary);
  border-bottom: 2px solid var(--border);
  padding-bottom: 8px;
  margin-bottom: 16px;
}
.bd-layout-horizontal {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 0;
  flex-wrap: wrap;
}
.bd-layout-vertical {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 0;
}
.bd-layout-grid {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 0;
}
.bd-row {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 0;
  flex-wrap: wrap;
}
.bd-box {
  border-radius: 10px;
  padding: 10px 16px;
  border: 2px solid;
  text-align: center;
  min-width: 80px;
  box-shadow: 0 2px 8px rgba(0,0,0,0.06);
}
.bd-box-header {
  font-family: Inter, Arial, sans-serif;
  font-weight: 700;
  font-size: 0.9em;
  margin-bottom: 4px;
}
.bd-box-line {
  font-family: Inter, Arial, sans-serif;
  font-size: 0.82em;
  line-height: 1.4;
}
.bd-c0 { background: #dbeafe; border-color: #2563eb; color: #1e40af; }
.bd-c1 { background: #dcfce7; border-color: #16a34a; color: #166534; }
.bd-c2 { background: #fce7f3; border-color: #db2777; color: #9d174d; }
.bd-c3 { background: #fef3c7; border-color: #d97706; color: #92400e; }
.bd-c4 { background: #e0e7ff; border-color: #4f46e5; color: #3730a3; }
.bd-c5 { background: #ede9fe; border-color: #7c3aed; color: #5b21b6; }
.bd-c6 { background: #ccfbf1; border-color: #0d9488; color: #115e59; }
.bd-c7 { background: #fee2e2; border-color: #dc2626; color: #991b1b; }
[data-theme="dark"] .bd-c0 { background: #1e3a5f; border-color: #60a5fa; color: #93c5fd; }
[data-theme="dark"] .bd-c1 { background: #14532d; border-color: #4ade80; color: #86efac; }
[data-theme="dark"] .bd-c2 { background: #500724; border-color: #f472b6; color: #f9a8d4; }
[data-theme="dark"] .bd-c3 { background: #451a03; border-color: #fbbf24; color: #fde68a; }
[data-theme="dark"] .bd-c4 { background: #312e81; border-color: #818cf8; color: #a5b4fc; }
[data-theme="dark"] .bd-c5 { background: #4c1d95; border-color: #a78bfa; color: #c4b5fd; }
[data-theme="dark"] .bd-c6 { background: #134e4a; border-color: #2dd4bf; color: #5eead4; }
[data-theme="dark"] .bd-c7 { background: #450a0a; border-color: #f87171; color: #fca5a5; }
.bd-arrow {
  display: flex;
  align-items: center;
  justify-content: center;
  color: #6366f1;
  font-size: 1.1em;
  padding: 4px 6px;
  flex-shrink: 0;
}
[data-theme="dark"] .bd-arrow { color: #818cf8; }
.bd-arrow-down { padding: 6px 0; }
.bd-container { text-align: left; }
.bd-text-line {
  font-family: 'JetBrains Mono', 'Fira Code', monospace;
  font-size: 0.85em;
  line-height: 1.6;
  padding: 2px 0;
  color: var(--text);
}
@media (max-width: 640px) {
  .bd-layout-horizontal { flex-direction: column; }
  .bd-row { flex-direction: column; }
  .bd-arrow-right { transform: rotate(90deg); }
}

/* ── Tree Diagrams ── */
.tree-diagram {
  background: linear-gradient(145deg, #f0fdf4, #ecfdf5);
  border: 1px solid #86efac;
  border-radius: 12px;
  padding: 20px 24px;
  margin: 1.5em 0;
  box-shadow: 0 4px 16px rgba(0,0,0,0.06);
  text-align: left;
}
[data-theme="dark"] .tree-diagram {
  background: linear-gradient(145deg, #052e16, #14532d);
  border-color: #166534;
}
.tree-content { font-family: 'JetBrains Mono', 'Fira Code', monospace; font-size: 14px; }
.tree-line { padding: 2px 0; white-space: nowrap; line-height: 1.6; }
.tree-line .tc { color: #16a34a; }
[data-theme="dark"] .tree-line .tc { color: #4ade80; }
.tree-icon { margin: 0 6px; font-size: 15px; vertical-align: middle; }
.tree-name { color: var(--text); }
.tree-dir .tree-name { font-weight: 600; }

/* ── Profile Cards ── */
.profile-cards {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 16px;
  margin: 1.5em 0;
}
@media (max-width: 640px) {
  .profile-cards { grid-template-columns: 1fr; }
}
.profile-card {
  background: var(--bg);
  border: 1px solid var(--border);
  border-top: 4px solid var(--pc-accent, #3b82f6);
  border-radius: 12px;
  padding: 24px 20px 20px;
  box-shadow: 0 2px 12px rgba(0,0,0,0.06);
  transition: transform 0.2s, box-shadow 0.2s;
}
.profile-card:hover {
  transform: translateY(-2px);
  box-shadow: 0 6px 20px rgba(0,0,0,0.1);
}
[data-theme="dark"] .profile-card {
  background: var(--bg-secondary);
  box-shadow: 0 2px 12px rgba(0,0,0,0.2);
}
[data-theme="dark"] .profile-card:hover {
  box-shadow: 0 6px 20px rgba(0,0,0,0.35);
}
.pc-icon { font-size: 28px; margin-bottom: 8px; }
.pc-title {
  font-family: 'Inter', var(--font-heading);
  font-weight: 700;
  font-size: 1rem;
  text-transform: uppercase;
  letter-spacing: 0.5px;
  color: var(--pc-accent, #3b82f6);
  margin-bottom: 10px;
}
.pc-quote {
  font-style: italic;
  color: var(--text-secondary);
  font-size: 0.92rem;
  line-height: 1.5;
  margin-bottom: 14px;
  padding-left: 12px;
  border-left: 3px solid var(--pc-accent, #3b82f6);
}
.pc-label {
  font-family: 'Inter', var(--font-heading);
  font-weight: 600;
  font-size: 0.78rem;
  text-transform: uppercase;
  letter-spacing: 0.8px;
  color: var(--text-secondary);
  margin-bottom: 6px;
}
.pc-path {
  list-style: none;
  padding: 0;
  margin: 0;
  font-size: 0.88rem;
}
.pc-path li {
  padding: 3px 0 3px 18px;
  position: relative;
  color: var(--text);
}
.pc-path li::before {
  content: '\25B8';
  position: absolute;
  left: 0;
  color: var(--pc-accent, #3b82f6);
  font-size: 0.8em;
}
.pc-detail {
  color: var(--text-secondary);
  font-size: 0.85em;
}

/* ── Author Card ── */
.author-card {
  display: flex;
  align-items: flex-start;
  gap: 24px;
  background: linear-gradient(135deg, var(--bg), var(--bg-secondary));
  border: 1px solid var(--border);
  border-radius: 16px;
  padding: 28px;
  margin: 1.5em 0 2em;
  box-shadow: 0 4px 16px rgba(0,0,0,0.06);
}
[data-theme="dark"] .author-card {
  box-shadow: 0 4px 16px rgba(0,0,0,0.25);
}
.author-avatar {
  flex-shrink: 0;
  width: 80px;
  height: 80px;
  border-radius: 50%;
  background: linear-gradient(135deg, var(--red), #0060B6);
  display: flex;
  align-items: center;
  justify-content: center;
  font-family: 'Inter', var(--font-heading);
  font-weight: 800;
  font-size: 28px;
  color: #fff;
  letter-spacing: 1px;
  box-shadow: 0 2px 8px rgba(190,0,39,0.25);
}
.author-info { flex: 1; }
.author-name {
  font-family: 'Inter', var(--font-heading);
  font-weight: 700;
  font-size: 1.3em;
  margin: 0 0 4px;
  color: var(--text);
}
.author-role {
  font-size: 0.95em;
  color: var(--text-secondary);
  margin-bottom: 12px;
}
.author-links {
  display: flex;
  gap: 12px;
  margin-top: 12px;
}
.author-links a {
  display: inline-flex;
  align-items: center;
  gap: 5px;
  padding: 6px 14px;
  border-radius: 6px;
  font-size: 0.85em;
  font-weight: 600;
  text-decoration: none;
  background: var(--bg-secondary);
  border: 1px solid var(--border);
  color: var(--text);
  transition: all var(--transition);
}
.author-links a:hover {
  background: var(--red);
  color: #fff;
  border-color: var(--red);
}
@media (max-width: 480px) {
  .author-card { flex-direction: column; align-items: center; text-align: center; }
  .author-links { justify-content: center; }
}

/* ── Ecosystem Grid ── */
.ecosystem-grid {
  margin: 1.5em 0;
  display: flex;
  flex-direction: column;
  gap: 16px;
}
.eco-section {
  background: var(--bg);
  border: 1px solid var(--border);
  border-left: 4px solid var(--eco-accent, #3b82f6);
  border-radius: 10px;
  padding: 16px 18px;
  box-shadow: 0 2px 8px rgba(0,0,0,0.04);
}
[data-theme="dark"] .eco-section {
  background: var(--bg-secondary);
  box-shadow: 0 2px 8px rgba(0,0,0,0.2);
}
.eco-header {
  font-family: 'Inter', var(--font-heading);
  font-weight: 700;
  font-size: 0.85rem;
  text-transform: uppercase;
  letter-spacing: 1px;
  color: var(--eco-accent, #3b82f6);
  margin-bottom: 12px;
}
.eco-icon { font-size: 1em; margin-right: 4px; }
.eco-cards {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(180px, 1fr));
  gap: 10px;
}
.eco-card {
  background: var(--bg-secondary);
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 12px 14px;
  transition: transform 0.15s, box-shadow 0.15s;
}
.eco-card:hover {
  transform: translateY(-1px);
  box-shadow: 0 4px 12px rgba(0,0,0,0.08);
}
[data-theme="dark"] .eco-card {
  background: rgba(255,255,255,0.04);
}
[data-theme="dark"] .eco-card:hover {
  box-shadow: 0 4px 12px rgba(0,0,0,0.3);
}
.eco-card-title {
  font-family: 'JetBrains Mono', monospace;
  font-weight: 600;
  font-size: 0.9rem;
  color: var(--text);
  margin-bottom: 2px;
}
.eco-card-sub {
  font-size: 0.78rem;
  color: var(--text-secondary);
  margin-bottom: 6px;
}
.eco-card-list {
  list-style: none;
  padding: 0;
  margin: 6px 0 0;
  font-size: 0.8rem;
  color: var(--text-secondary);
}
.eco-card-list li {
  padding: 1px 0 1px 14px;
  position: relative;
}
.eco-card-list li::before {
  content: '\2022';
  position: absolute;
  left: 0;
  color: var(--eco-accent, #3b82f6);
}
@media (max-width: 480px) {
  .eco-cards { grid-template-columns: 1fr; }
}

/* ── Tables ── */
.table-wrapper {
  overflow-x: auto;
  margin: 1em 0;
  border-radius: var(--radius);
  border: 1px solid var(--border);
}
table {
  width: 100%;
  border-collapse: collapse;
  font-size: 0.92em;
}
thead {
  background: var(--dark);
  color: #fff;
}
[data-theme="dark"] thead {
  background: #21262d;
}
th {
  font-family: Inter, Arial, sans-serif;
  font-weight: 600;
  padding: 10px 14px;
  text-align: left;
  font-size: 0.9em;
}
td {
  padding: 10px 14px;
  border-top: 1px solid var(--border);
}
tbody tr:nth-child(even) {
  background: var(--bg-secondary);
}
tbody tr:hover {
  background: color-mix(in srgb, var(--blue) 8%, var(--bg));
}

/* ── Prev/Next Nav ── */
.chapter-nav {
  display: flex;
  gap: 16px;
  margin-top: 3em;
  padding-top: 2em;
  border-top: 1px solid var(--border);
}
.chapter-nav a {
  flex: 1;
  display: block;
  padding: 16px 20px;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  text-decoration: none;
  transition: all var(--transition);
  font-family: Inter, Arial, sans-serif;
}
.chapter-nav a:hover {
  border-color: var(--blue);
  box-shadow: var(--shadow);
}
.chapter-nav .nav-label {
  font-size: 12px;
  color: var(--text-secondary);
  text-transform: uppercase;
  letter-spacing: 0.05em;
}
.chapter-nav .nav-title {
  font-size: 15px;
  font-weight: 600;
  color: var(--text);
  margin-top: 4px;
}
.nav-next { text-align: right; }

/* ── Search Modal ── */
.search-overlay {
  display: none;
  position: fixed;
  inset: 0;
  background: rgba(0,0,0,0.5);
  z-index: 200;
  align-items: flex-start;
  justify-content: center;
  padding-top: 15vh;
}
.search-overlay.open { display: flex; }
.search-modal {
  background: var(--bg);
  border: 1px solid var(--border);
  border-radius: 12px;
  width: 560px;
  max-width: 90vw;
  max-height: 60vh;
  box-shadow: var(--shadow-lg);
  display: flex;
  flex-direction: column;
  overflow: hidden;
}
.search-input-wrap {
  display: flex;
  align-items: center;
  padding: 12px 16px;
  border-bottom: 1px solid var(--border);
  gap: 10px;
}
.search-input-wrap svg { flex-shrink: 0; color: var(--text-secondary); }
.search-input {
  flex: 1;
  border: none;
  background: none;
  font-size: 16px;
  color: var(--text);
  outline: none;
  font-family: Inter, Arial, sans-serif;
}
.search-input::placeholder { color: var(--text-secondary); }
.search-results {
  overflow-y: auto;
  padding: 8px;
  flex: 1;
}
.search-result {
  display: block;
  padding: 10px 12px;
  border-radius: 6px;
  text-decoration: none;
  transition: background var(--transition);
  cursor: pointer;
}
.search-result:hover, .search-result.active {
  background: var(--bg-secondary);
}
.search-result-title {
  font-family: Inter, Arial, sans-serif;
  font-size: 14px;
  font-weight: 600;
  color: var(--text);
}
.search-result-chapter {
  font-size: 12px;
  color: var(--text-secondary);
}
.search-result-preview {
  font-size: 13px;
  color: var(--text-secondary);
  margin-top: 2px;
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
}
.search-empty {
  padding: 20px;
  text-align: center;
  color: var(--text-secondary);
  font-family: Inter, Arial, sans-serif;
  font-size: 14px;
}

/* ── Back to Top ── */
.back-to-top {
  position: fixed;
  bottom: 32px;
  right: 32px;
  width: 40px; height: 40px;
  border-radius: 50%;
  background: var(--blue);
  color: #fff;
  border: none;
  cursor: pointer;
  font-size: 18px;
  display: flex;
  align-items: center;
  justify-content: center;
  box-shadow: var(--shadow-lg);
  opacity: 0;
  transform: translateY(10px);
  transition: opacity 0.3s, transform 0.3s;
  z-index: 50;
}
.back-to-top.visible { opacity: 1; transform: translateY(0); }
.back-to-top:hover { background: var(--red); }

/* ── Reading Time Badge ── */
.reading-time {
  font-family: Inter, Arial, sans-serif;
  font-size: 13px;
  color: var(--text-secondary);
  margin-bottom: 1.5em;
  display: flex;
  align-items: center;
  gap: 6px;
}

/* ── Index Page — O'Reilly-inspired Cover ── */
.hero {
  text-align: center;
  padding: 0;
  background: var(--bg);
  border-bottom: 1px solid var(--border);
}
.hero-cover {
  max-width: 680px;
  margin: 40px auto 32px;
  border: 2px solid #333;
  border-radius: 4px;
  overflow: hidden;
  box-shadow: 0 8px 32px rgba(0,0,0,0.12), 0 2px 8px rgba(0,0,0,0.08);
  background: #fff;
}
[data-theme="dark"] .hero-cover {
  border-color: #555;
  box-shadow: 0 8px 32px rgba(0,0,0,0.4);
  background: #1a1a2e;
}
/* Top colored band */
.cover-band {
  background: var(--red);
  padding: 14px 24px;
  display: flex;
  align-items: center;
  justify-content: center;
}
.cover-edition {
  font-family: 'Inter', Arial, sans-serif;
  font-size: 0.72rem;
  font-weight: 600;
  color: #fff;
  letter-spacing: 1.5px;
  text-transform: uppercase;
}
/* Logo area */
.cover-logo-area {
  padding: 48px 24px 44px;
  background: linear-gradient(180deg, #f8f9fa 0%, #fff 100%);
  display: flex;
  justify-content: center;
  align-items: center;
  border-bottom: 1px solid #e5e7eb;
}
[data-theme="dark"] .cover-logo-area {
  background: linear-gradient(180deg, #16213e 0%, #1a1a2e 100%);
  border-bottom-color: #333;
}
.hero-logo {
  width: 180px;
  height: 180px;
  object-fit: contain;
  background: transparent;
}
/* Title section */
.cover-title-area {
  padding: 36px 32px 24px;
}
.cover-title {
  font-family: Georgia, 'Times New Roman', serif;
  font-size: 2.4em;
  font-weight: 700;
  color: #111;
  line-height: 1.15;
  margin: 0 0 10px;
  border: none;
}
[data-theme="dark"] .cover-title {
  color: #f0f0f0;
}
.cover-subtitle {
  font-family: Georgia, 'Times New Roman', serif;
  font-size: 1.1rem;
  font-style: italic;
  color: #555;
  line-height: 1.5;
  margin: 0;
}
[data-theme="dark"] .cover-subtitle {
  color: #999;
}
/* Divider line */
.cover-divider {
  width: 60px;
  height: 3px;
  background: var(--red);
  margin: 20px auto;
  border-radius: 2px;
}
/* Bottom section */
.cover-bottom {
  padding: 20px 32px 28px;
  border-top: 1px solid #e5e7eb;
  background: #fafafa;
}
[data-theme="dark"] .cover-bottom {
  border-top-color: #333;
  background: #111827;
}
.cover-author {
  font-family: 'Inter', Arial, sans-serif;
  font-weight: 600;
  font-size: 1.05rem;
  color: #333;
  margin-bottom: 2px;
}
[data-theme="dark"] .cover-author { color: #ddd; }
.cover-tag {
  font-family: 'Inter', Arial, sans-serif;
  font-size: 0.72rem;
  color: #888;
  text-transform: uppercase;
  letter-spacing: 1px;
}
/* Stats bar */
.cover-stats {
  display: flex;
  justify-content: center;
  gap: 24px;
  padding: 10px 24px 14px;
  font-family: 'Inter', Arial, sans-serif;
  font-size: 0.78rem;
  color: #888;
}
.cover-stat {
  display: flex;
  align-items: center;
  gap: 5px;
}
.cover-stat strong {
  color: var(--text);
  font-weight: 700;
}
/* CTA below cover */
.hero-cta {
  max-width: 680px;
  margin: 0 auto;
  padding: 0 20px 40px;
  display: flex;
  justify-content: center;
  align-items: center;
  gap: 12px;
  flex-wrap: wrap;
}
.hero .start-btn {
  display: inline-block;
  padding: 10px 28px;
  background: var(--red);
  color: #fff;
  border-radius: 6px;
  font-family: 'Inter', Arial, sans-serif;
  font-weight: 600;
  font-size: 14px;
  text-decoration: none;
  transition: all var(--transition);
  box-shadow: 0 3px 10px rgba(190,0,39,0.25);
  flex: 1;
  max-width: 280px;
  text-align: center;
}
.hero .start-btn:hover {
  transform: translateY(-2px);
  text-decoration: none;
}
.hero .start-btn:first-child:hover {
  background: #a00020;
  box-shadow: 0 5px 16px rgba(190,0,39,0.35);
}
.hero .start-btn-alt {
  background: var(--blue);
  box-shadow: 0 3px 10px rgba(0,96,182,0.25);
}
.hero .start-btn-alt:hover {
  background: #004a8f;
  box-shadow: 0 5px 16px rgba(0,96,182,0.35);
}
.hero-version {
  width: 100%;
  margin-top: 4px;
  font-family: 'Inter', Arial, sans-serif;
  font-size: 0.8rem;
  color: var(--text-secondary);
  text-align: center;
}
@media (max-width: 560px) {
  .hero-cover { margin: 20px 16px 24px; }
  .cover-title { font-size: 1.6em; }
  .hero-logo { width: 100px; height: 100px; }
}

/* Learning Path */
.learning-path {
  max-width: 900px;
  margin: 3em auto;
  padding: 0 20px;
}
.learning-path h2 {
  text-align: center;
  border: none;
  margin-bottom: 1.5em;
}
.path-nodes {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  gap: 0;
  position: relative;
}
.path-node {
  display: flex;
  flex-direction: column;
  align-items: center;
  width: 120px;
  text-align: center;
  position: relative;
  padding: 0 8px;
}
.path-node::after {
  content: '';
  position: absolute;
  top: 18px;
  left: calc(50% + 18px);
  width: calc(100% - 36px);
  height: 2px;
  background: var(--border);
}
.path-node:last-child::after { display: none; }
.path-dot {
  width: 36px; height: 36px;
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  font-family: Inter, Arial, sans-serif;
  font-weight: 700;
  font-size: 14px;
  color: #fff;
  margin-bottom: 8px;
  position: relative;
  z-index: 1;
}
.path-label {
  font-family: Inter, Arial, sans-serif;
  font-size: 11px;
  color: var(--text-secondary);
  line-height: 1.3;
}

/* Chapter Cards */
.parts-grid {
  max-width: 1000px;
  margin: 0 auto;
  padding: 0 20px 60px;
}
.part-section {
  margin-bottom: 2.5em;
}
.part-section h3 {
  font-family: Inter, Arial, sans-serif;
  font-size: 1.1em;
  color: var(--text-secondary);
  border-bottom: 1px solid var(--border);
  padding-bottom: 0.5em;
  margin-bottom: 1em;
  margin-top: 0;
}
.cards-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(260px, 1fr));
  gap: 12px;
}
.chapter-card {
  display: flex;
  align-items: center;
  gap: 12px;
  padding: 14px 16px;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  text-decoration: none;
  transition: all var(--transition);
  background: var(--bg);
}
.chapter-card:hover {
  border-color: var(--blue);
  box-shadow: var(--shadow);
  text-decoration: none;
  transform: translateY(-1px);
}
.card-num {
  font-family: Inter, Arial, sans-serif;
  font-weight: 700;
  font-size: 14px;
  color: var(--blue);
  min-width: 28px;
}
.card-info { flex: 1; min-width: 0; }
.card-title {
  font-family: Inter, Arial, sans-serif;
  font-size: 14px;
  font-weight: 600;
  color: var(--text);
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}
.card-meta {
  font-family: Inter, Arial, sans-serif;
  font-size: 12px;
  color: var(--text-secondary);
  margin-top: 2px;
}
.card-check {
  font-size: 16px;
  opacity: 0;
  transition: opacity var(--transition);
}
.chapter-card.visited .card-check { opacity: 1; }

/* ── About Page ── */
.about-content { max-width: var(--content-max); margin: 0 auto; padding: 40px 32px 80px; }

/* ── Responsive ── */
@media (max-width: 1024px) {
  .sidebar {
    transform: translateX(-100%);
  }
  .sidebar.open {
    transform: translateX(0);
    box-shadow: var(--shadow-lg);
  }
  .sidebar-overlay.open {
    display: block;
  }
  .main {
    margin-left: 0;
  }
  .hamburger {
    display: block;
  }
}

@media (max-width: 640px) {
  .content, .about-content {
    padding: 24px 16px 60px;
  }
  h1 { font-size: 1.6em; }
  h2 { font-size: 1.3em; }
  body { font-size: 16px; }
  .chapter-nav {
    flex-direction: column;
  }
  .cover-title { font-size: 1.5em; }
  .path-nodes { gap: 4px; }
  .path-node { width: 80px; }
  .path-dot { width: 28px; height: 28px; font-size: 12px; }
  .cards-grid {
    grid-template-columns: 1fr;
  }
  .search-modal { max-height: 80vh; }
}