/* =========================================================
   Engineermaxxing — Global Stylesheet
   ========================================================= */

/* ── Custom Properties ────────────────────────────────── */
:root {
  --bg:          #080809;
  --bg-elevated: #0f0f13;
  --bg-card:     #111116;
  --bg-code:     #0c0c14;
  --bg-viz:      #0e0e18;
  --border:      #1f1f2b;
  --border-hover:#2d2d3f;

  --text:        #d6d6e8;
  --text-dim:    #9898b0;
  --text-muted:  #5c5c78;

  --purple:  #8b5cf6;
  --blue:    #3b82f6;
  --green:   #10b981;
  --teal:    #14b8a6;
  --orange:  #f59e0b;
  --red:     #ef4444;
  --cyan:    #06b6d4;
  --pink:    #ec4899;

  --font:      'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
  --font-mono: 'JetBrains Mono', 'Fira Code', 'Cascadia Code', monospace;

  --radius:  10px;
  --radius-lg: 16px;
  --transition: 180ms ease;
  --transition-slow: 360ms ease;
  --container: 1220px;
}

/* ── Light Theme ──────────────────────────────────────── */
[data-theme="light"] {
  --bg:          #f4f4f8;
  --bg-elevated: #ffffff;
  --bg-card:     #ffffff;
  --bg-code:     #1e1e2e;
  --bg-viz:      #f0f0f8;
  --border:      #c8c8d8;
  --border-hover:#9898b0;

  --text:        #111122;
  --text-dim:    #3a3a58;
  --text-muted:  #5a5a78;

  --purple:  #6d28d9;
  --blue:    #1d4ed8;
  --green:   #047857;
  --teal:    #0f766e;
  --orange:  #b45309;
  --red:     #b91c1c;
  --cyan:    #0e7490;
  --pink:    #be185d;
}

/* ── Light: Header & Navigation ──────────────────── */
[data-theme="light"] .site-header.scrolled {
  background: rgba(244, 244, 248, 0.92);
  border-color: var(--border);
}
[data-theme="light"] .article-page-header {
  background: rgba(244, 244, 248, 0.96);
  border-color: var(--border);
}
[data-theme="light"] .site-logo:hover { color: #000; }
[data-theme="light"] .nav-link { color: var(--text-dim); }
[data-theme="light"] .nav-link:hover { color: #111122; }
[data-theme="light"] .breadcrumb a { color: var(--text-dim); }
[data-theme="light"] .breadcrumb a:hover { color: #111122; }

[data-theme="light"] #bg-canvas { opacity: 0.15; }

/* ── Light: Callouts ─────────────────────────────── */
[data-theme="light"] .callout.info {
  background: rgba(29, 78, 216, 0.06);
  border-color: rgba(29, 78, 216, 0.25);
  color: var(--text-dim);
}
[data-theme="light"] .callout.info .callout-header { color: var(--blue); }
[data-theme="light"] .callout.insight {
  background: rgba(109, 40, 217, 0.06);
  border-color: rgba(109, 40, 217, 0.25);
  color: var(--text-dim);
}
[data-theme="light"] .callout.insight .callout-header { color: var(--purple); }
[data-theme="light"] .callout.math {
  background: rgba(4, 120, 87, 0.06);
  border-color: rgba(4, 120, 87, 0.25);
  color: var(--text-dim);
}
[data-theme="light"] .callout.math .callout-header { color: var(--green); }
[data-theme="light"] .callout p,
[data-theme="light"] .callout li,
[data-theme="light"] .callout em,
[data-theme="light"] .callout span { color: var(--text-dim); }
[data-theme="light"] .callout strong { color: var(--text); }

/* ── Light: Code blocks ──────────────────────────── */
[data-theme="light"] .code-block {
  border-color: var(--border);
}
[data-theme="light"] .code-block-header {
  background: #2d2d3f;
  border-color: #2d2d3f;
  color: #d6d6e8;
}
[data-theme="light"] .code-block-header .code-lang { color: #9898b0; }
[data-theme="light"] .code-block-header .copy-btn {
  color: #9898b0;
  border-color: rgba(255,255,255,0.15);
}
[data-theme="light"] pre[class*="language-"] {
  background: #1e1e2e !important;
  color: #d6d6e8 !important;
}
[data-theme="light"] code[class*="language-"] {
  color: #d6d6e8 !important;
}

/* ── Light: Inline code ──────────────────────────── */
[data-theme="light"] :not(pre) > code {
  background: rgba(109, 40, 217, 0.08);
  color: #5b21b6;
  border: 1px solid rgba(109, 40, 217, 0.15);
  padding: 0.1em 0.35em;
  border-radius: 4px;
  font-size: 0.88em;
}

/* ── Light: Tables ───────────────────────────────── */
[data-theme="light"] .data-table {
  border-color: var(--border);
}
[data-theme="light"] .data-table th {
  background: #e8e8f2;
  color: var(--text);
  border-color: var(--border);
}
[data-theme="light"] .data-table td {
  border-color: var(--border);
  color: var(--text-dim);
}
[data-theme="light"] .data-table td strong { color: var(--text); }
[data-theme="light"] .data-table tr:hover td {
  background: rgba(109, 40, 217, 0.04);
}

/* ── Light: Math blocks ──────────────────────────── */
[data-theme="light"] .math-block {
  background: rgba(109, 40, 217, 0.05);
  border-color: rgba(109, 40, 217, 0.2);
  color: var(--text);
}

/* ── Light: Viz containers ───────────────────────── */
[data-theme="light"] .viz-wrap {
  background: var(--bg-card);
  border-color: var(--border);
  box-shadow: 0 1px 4px rgba(0,0,0,0.06);
}
[data-theme="light"] .viz-header { border-color: var(--border); }
[data-theme="light"] .viz-title { color: var(--text); }
[data-theme="light"] .viz-tag {
  background: rgba(109, 40, 217, 0.08);
  color: #5b21b6;
  border-color: rgba(109, 40, 217, 0.2);
}
[data-theme="light"] .viz-btn {
  background: rgba(0,0,0,0.04);
  border-color: var(--border);
  color: var(--text-dim);
}
[data-theme="light"] .viz-btn:hover {
  background: rgba(0,0,0,0.08);
  color: var(--text);
}
[data-theme="light"] .viz-btn.primary {
  background: var(--purple);
  border-color: var(--purple);
  color: #fff;
}
[data-theme="light"] .viz-status { color: var(--text-muted); }

/* ── Light: Cards ────────────────────────────────── */
[data-theme="light"] .article-card {
  background: var(--bg-card);
  border-color: var(--border);
  box-shadow: 0 1px 3px rgba(0,0,0,0.06);
}
[data-theme="light"] .article-card:hover {
  border-color: var(--border-hover);
  box-shadow: 0 8px 30px rgba(0,0,0,0.1);
}
[data-theme="light"] .card-title { color: var(--text); }
[data-theme="light"] .card-description { color: var(--text-dim); }
[data-theme="light"] .card-tag {
  background: rgba(109, 40, 217, 0.06);
  border-color: rgba(109, 40, 217, 0.15);
  color: #5b21b6;
}

/* ── Light: Series cards (main index) ────────────── */
[data-theme="light"] .series-card {
  box-shadow: 0 1px 3px rgba(0,0,0,0.06);
}
[data-theme="light"] .series-card:hover {
  box-shadow: 0 8px 30px rgba(0,0,0,0.1);
}
[data-theme="light"] .series-topic {
  background: rgba(0,0,0,0.03);
  border-color: var(--border);
  color: var(--text-dim);
}

/* ── Light: TOC sidebar ──────────────────────────── */
[data-theme="light"] .toc-sidebar {
  border-color: var(--border);
}
[data-theme="light"] .toc-heading { color: var(--text-muted); }
[data-theme="light"] .toc-link {
  color: var(--text-muted);
  border-color: transparent;
}
[data-theme="light"] .toc-link:hover { color: var(--text); }
[data-theme="light"] .toc-link.active {
  color: var(--purple);
  border-color: var(--purple);
}

/* ── Light: Article body ─────────────────────────── */
[data-theme="light"] .article-body p { color: var(--text-dim); }
[data-theme="light"] .article-body h2,
[data-theme="light"] .article-body h3 { color: var(--text); }
[data-theme="light"] .article-body strong { color: var(--text); }
[data-theme="light"] .article-body a { color: var(--purple); }
[data-theme="light"] .article-body li { color: var(--text-dim); }
[data-theme="light"] .article-subtitle { color: var(--text-dim); }
[data-theme="light"] .article-meta .meta-item { color: var(--text-muted); }

/* ── Light: Reading progress ─────────────────────── */
[data-theme="light"] .reading-progress {
  background: var(--purple);
}

/* ── Light: Footer ───────────────────────────────── */
[data-theme="light"] .site-footer {
  border-color: var(--border);
}
[data-theme="light"] .footer-text { color: var(--text-muted); }
[data-theme="light"] .footer-link { color: var(--purple); }

/* ── Light: Hero ─────────────────────────────────── */
[data-theme="light"] .hero-description { color: var(--text-dim); }
[data-theme="light"] .hero-eyebrow { color: var(--text-muted); }
[data-theme="light"] .stat-value { color: var(--text); }
[data-theme="light"] .stat-label { color: var(--text-muted); }

/* ── Light: References ───────────────────────────── */
[data-theme="light"] .references-list { color: var(--text-dim) !important; }
[data-theme="light"] .references-list a { color: var(--purple) !important; }

/* ── Light: Canvas override hint ─────────────────── */
/* Canvas visualizations use hardcoded colors in JS.
   We expose a CSS custom property that JS can read: */
[data-theme="light"] { --canvas-text: #3a3a58; --canvas-text-dim: #5a5a78; --canvas-bg: #f0f0f8; }

/* ── Theme Toggle Button ─────────────────────────── */
.theme-toggle {
  background: rgba(255,255,255,0.06);
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 0.4rem 0.6rem;
  color: var(--text-dim);
  font-size: 0.9rem;
  line-height: 1;
  cursor: pointer;
  transition: color var(--transition), border-color var(--transition), background var(--transition), box-shadow var(--transition);
  display: flex;
  align-items: center;
  gap: 0.3rem;
}
.theme-toggle:hover {
  color: var(--text);
  border-color: var(--border-hover);
  background: rgba(255,255,255,0.1);
}
[data-theme="light"] .theme-toggle {
  background: rgba(0,0,0,0.05);
  border-color: #b0b0c0;
  color: #3a3a58;
}
[data-theme="light"] .theme-toggle:hover {
  background: rgba(0,0,0,0.1);
  border-color: #8888a0;
  color: #111122;
  box-shadow: 0 1px 4px rgba(0,0,0,0.08);
}
.theme-toggle .icon-sun,
.theme-toggle .icon-moon { width: 16px; height: 16px; }
/* Dark mode: show sun icon (click to switch to light) */
/* Light mode: show moon icon (click to switch to dark) */
[data-theme="light"] .theme-toggle .icon-sun { display: none; }
:not([data-theme="light"]) .theme-toggle .icon-moon { display: none; }

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

html {
  font-size: 16px;
  scroll-behavior: smooth;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

body {
  font-family: var(--font);
  background: var(--bg);
  color: var(--text);
  line-height: 1.7;
  min-height: 100vh;
  overflow-x: hidden;
}

a { color: inherit; text-decoration: none; }
img { display: block; max-width: 100%; }
button { font-family: inherit; cursor: pointer; }
code, pre { font-family: var(--font-mono); }

/* ── Utility ──────────────────────────────────────────── */
.gradient-text {
  background: linear-gradient(135deg, var(--purple) 0%, var(--blue) 100%);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}
[data-theme="light"] .gradient-text {
  background: linear-gradient(135deg, #4c1d95 0%, #1e3a8a 100%) !important;
  -webkit-background-clip: text !important;
  -webkit-text-fill-color: transparent !important;
  background-clip: text !important;
}
/* Override ALL -webkit-text-fill-color: transparent in light mode hero titles */
[data-theme="light"] [style*="text-fill-color"] {
  -webkit-text-fill-color: transparent !important;
  background: linear-gradient(135deg, #4c1d95 0%, #1e3a8a 100%) !important;
  -webkit-background-clip: text !important;
  background-clip: text !important;
}
/* Catch overview titles that use inline gradient styles */
[data-theme="light"] .overview-title .gradient-text,
[data-theme="light"] .hero-title .gradient-text,
[data-theme="light"] h1 .gradient-text,
[data-theme="light"] h1.gradient-text {
  background: linear-gradient(135deg, #4c1d95 0%, #1e3a8a 100%) !important;
  -webkit-background-clip: text !important;
  -webkit-text-fill-color: transparent !important;
  background-clip: text !important;
}
/* Also catch hero title lines that aren't gradient-text but have light colors */
[data-theme="light"] .hero-title,
[data-theme="light"] .overview-title,
[data-theme="light"] .title-line { color: var(--text); }

.container {
  max-width: var(--container);
  margin-inline: auto;
  padding-inline: 2rem;
}

/* ══════════════════════════════════════════════════════════
   LANDING PAGE
   ══════════════════════════════════════════════════════════ */

/* ── Canvas Background ────────────────────────────────── */
#bg-canvas {
  position: fixed;
  inset: 0;
  width: 100%;
  height: 100%;
  pointer-events: none;
  z-index: 0;
  opacity: 0.6;
}

/* ── Site Header ──────────────────────────────────────── */
.site-header {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 100;
  border-bottom: 1px solid transparent;
  transition: border-color var(--transition), background var(--transition);
}

.site-header.scrolled {
  background: rgba(8, 8, 9, 0.85);
  border-color: var(--border);
  backdrop-filter: blur(20px);
  -webkit-backdrop-filter: blur(20px);
}

.header-inner {
  max-width: var(--container);
  margin-inline: auto;
  padding: 1.1rem 2rem;
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.site-logo {
  display: flex;
  align-items: center;
  gap: 0.6rem;
  font-size: 1rem;
  font-weight: 600;
  color: var(--text);
  letter-spacing: -0.01em;
  transition: color var(--transition);
}
.site-logo:hover { color: #fff; }

.logo-icon {
  font-size: 1.2rem;
  background: linear-gradient(135deg, var(--purple), var(--blue));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.header-nav { display: flex; gap: 1.5rem; align-items: center; }

.nav-link {
  font-size: 0.9rem;
  color: var(--text-dim);
  transition: color var(--transition);
}
.nav-link:hover { color: var(--text); }

/* ── Hero ─────────────────────────────────────────────── */
.hero {
  position: relative;
  z-index: 1;
  padding: 12rem 2rem 8rem;
  display: flex;
  align-items: center;
  justify-content: center;
  text-align: center;
}

.hero-content { max-width: 820px; }

.hero-eyebrow {
  display: inline-flex;
  align-items: center;
  gap: 0.6rem;
  font-size: 0.8rem;
  font-weight: 500;
  text-transform: uppercase;
  letter-spacing: 0.12em;
  color: var(--text-muted);
  margin-bottom: 1.5rem;
}

.eyebrow-dot {
  width: 6px;
  height: 6px;
  border-radius: 50%;
  background: var(--purple);
  box-shadow: 0 0 8px var(--purple);
  animation: pulse 2s ease-in-out infinite;
}

@keyframes pulse {
  0%, 100% { opacity: 1; transform: scale(1); }
  50% { opacity: 0.6; transform: scale(0.8); }
}

.hero-title {
  font-size: clamp(2.2rem, 7vw, 5rem);
  font-weight: 900;
  line-height: 1.15;
  letter-spacing: -0.03em;
  margin-bottom: 1.8rem;
  padding-bottom: 0.1em;
}

.title-line { display: block; }

.hero-description {
  font-size: 1.15rem;
  color: var(--text-dim);
  max-width: 580px;
  margin-inline: auto;
  margin-bottom: 3rem;
  line-height: 1.75;
}

.hero-stats {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 2rem;
}

.stat { text-align: center; }

.stat-value {
  display: block;
  font-size: 1.6rem;
  font-weight: 700;
  color: #fff;
  letter-spacing: -0.03em;
  line-height: 1;
  margin-bottom: 0.25rem;
}

.stat-label {
  font-size: 0.75rem;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--text-muted);
  font-weight: 500;
}

.stat-divider {
  width: 1px;
  height: 32px;
  background: var(--border);
}

/* ── Articles Section ─────────────────────────────────── */
.articles-section {
  position: relative;
  z-index: 1;
  padding: 0 2rem 8rem;
  max-width: var(--container);
  margin-inline: auto;
}

.section-label {
  font-size: 0.75rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.12em;
  color: var(--text-muted);
  margin-bottom: 2rem;
}

.articles-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(320px, 1fr));
  gap: 1px;
  background: var(--border);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  overflow: hidden;
}

/* ── Article Card ─────────────────────────────────────── */
.article-card {
  position: relative;
  background: var(--bg-card);
  padding: 2rem;
  transition: background var(--transition);
  display: flex;
  flex-direction: column;
  gap: 0.85rem;
}

.article-card:not(.coming-soon):hover {
  background: var(--bg-elevated);
}

.card-link-overlay {
  position: absolute;
  inset: 0;
  z-index: 1;
}

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

.card-number {
  font-size: 0.75rem;
  font-weight: 700;
  font-family: var(--font-mono);
  letter-spacing: 0.05em;
  color: var(--text-muted);
}

/* Color per article */
.article-card[data-color="purple"] .card-number { color: var(--purple); }
.article-card[data-color="blue"]   .card-number { color: var(--blue);   }
.article-card[data-color="green"]  .card-number { color: var(--green);  }
.article-card[data-color="teal"]   .card-number { color: var(--teal);   }
.article-card[data-color="orange"] .card-number { color: var(--orange); }
.article-card[data-color="red"]    .card-number { color: var(--red);    }
.article-card[data-color="cyan"]   .card-number { color: var(--cyan);   }
.article-card[data-color="pink"]   .card-number { color: var(--pink);   }

.card-tags { display: flex; gap: 0.4rem; }

.card-tag {
  font-size: 0.68rem;
  font-weight: 500;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--text-muted);
  background: rgba(255,255,255,0.04);
  border: 1px solid var(--border);
  padding: 0.2rem 0.55rem;
  border-radius: 20px;
}

.card-title {
  font-size: 1.15rem;
  font-weight: 700;
  letter-spacing: -0.02em;
  color: var(--text);
  line-height: 1.3;
}

.card-description {
  font-size: 0.875rem;
  color: var(--text-dim);
  line-height: 1.65;
  flex: 1;
}

.card-footer {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-top: 0.5rem;
  padding-top: 1.1rem;
  border-top: 1px solid var(--border);
}

.card-meta {
  font-size: 0.75rem;
  color: var(--text-muted);
  font-weight: 500;
}

.card-arrow {
  font-size: 0.85rem;
  font-weight: 600;
  color: var(--purple);
  transition: transform var(--transition), color var(--transition);
}

.article-card:not(.coming-soon):hover .card-arrow {
  transform: translateX(4px);
  color: #a78bfa;
}

.coming-soon { opacity: 0.45; pointer-events: none; }

.coming-soon-badge {
  font-size: 0.7rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--text-muted);
  border: 1px solid var(--border);
  padding: 0.2rem 0.65rem;
  border-radius: 20px;
}

/* ── Site Footer ──────────────────────────────────────── */
.site-footer {
  position: relative;
  z-index: 1;
  border-top: 1px solid var(--border);
  padding: 2rem;
}

.footer-inner {
  max-width: var(--container);
  margin-inline: auto;
  text-align: center;
}

.footer-text {
  font-size: 0.85rem;
  color: var(--text-muted);
}

.footer-link {
  color: var(--purple);
  transition: color var(--transition);
}
.footer-link:hover { color: #a78bfa; }

/* ══════════════════════════════════════════════════════════
   ARTICLE PAGE
   ══════════════════════════════════════════════════════════ */

/* ── Reading Progress Bar ─────────────────────────────── */
.reading-progress {
  position: fixed;
  top: 0;
  left: 0;
  height: 2px;
  background: linear-gradient(90deg, var(--purple), var(--blue));
  z-index: 200;
  width: 0%;
  transition: width 100ms linear;
}

/* ── Article Header ───────────────────────────────────── */
.article-page-header {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 100;
  background: rgba(8,8,9,0.9);
  border-bottom: 1px solid var(--border);
  backdrop-filter: blur(20px);
  -webkit-backdrop-filter: blur(20px);
}

.article-page-header .header-inner {
  max-width: 1400px;
}

.breadcrumb {
  display: flex;
  align-items: center;
  gap: 0.4rem;
  font-size: 0.82rem;
  color: var(--text-muted);
}

.breadcrumb a { transition: color var(--transition); }
.breadcrumb a:hover { color: var(--text); }
.breadcrumb-sep { color: var(--text-muted); }

/* ── Article Layout ───────────────────────────────────── */
.article-layout {
  display: grid;
  grid-template-columns: 260px 1fr;
  grid-template-rows: auto;
  max-width: 1400px;
  margin-inline: auto;
  padding-top: 64px;
  min-height: 100vh;
  gap: 0;
}

/* ── TOC Sidebar ──────────────────────────────────────── */
.toc-sidebar {
  position: sticky;
  top: 64px;
  height: calc(100vh - 64px);
  overflow-y: auto;
  padding: 3rem 0 3rem 2rem;
  border-right: 1px solid var(--border);
  scrollbar-width: thin;
  scrollbar-color: var(--border) transparent;
}

.toc-sidebar::-webkit-scrollbar { width: 4px; }
.toc-sidebar::-webkit-scrollbar-track { background: transparent; }
.toc-sidebar::-webkit-scrollbar-thumb { background: var(--border); border-radius: 4px; }

.toc-heading {
  font-size: 0.7rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.12em;
  color: var(--text-muted);
  margin-bottom: 1rem;
  padding-left: 1rem;
}

.toc-nav { list-style: none; }

.toc-item { margin: 0; }

.toc-link {
  display: block;
  padding: 0.35rem 1rem;
  font-size: 0.82rem;
  color: var(--text-muted);
  border-left: 2px solid transparent;
  transition: color var(--transition), border-color var(--transition), background var(--transition);
  border-radius: 0 var(--radius) var(--radius) 0;
  line-height: 1.4;
}

.toc-link:hover { color: var(--text-dim); }

.toc-link.active {
  color: var(--purple);
  border-left-color: var(--purple);
  background: rgba(139,92,246,0.08);
}

.toc-item.sub .toc-link { padding-left: 1.8rem; font-size: 0.78rem; }

/* ── Article Main ─────────────────────────────────────── */
.article-main {
  padding: 3.5rem 4rem 6rem;
  max-width: 860px;
  min-width: 0;
}

.article-header {
  margin-bottom: 3.5rem;
  padding-bottom: 2.5rem;
  border-bottom: 1px solid var(--border);
}

.article-eyebrow {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  margin-bottom: 1.2rem;
}

.article-number {
  font-size: 0.75rem;
  font-weight: 700;
  font-family: var(--font-mono);
  color: var(--purple);
  letter-spacing: 0.05em;
}

.article-category {
  font-size: 0.72rem;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  color: var(--text-muted);
  background: rgba(139,92,246,0.1);
  border: 1px solid rgba(139,92,246,0.2);
  padding: 0.2rem 0.6rem;
  border-radius: 20px;
  font-weight: 500;
}

.article-title {
  font-size: clamp(2rem, 4vw, 2.8rem);
  font-weight: 800;
  letter-spacing: -0.03em;
  line-height: 1.15;
  color: var(--text);
  margin-bottom: 1.2rem;
}

.article-subtitle {
  font-size: 1.1rem;
  color: var(--text-dim);
  line-height: 1.7;
  max-width: 640px;
  margin-bottom: 2rem;
}

.article-meta {
  display: flex;
  align-items: center;
  gap: 1.2rem;
  font-size: 0.82rem;
  color: var(--text-muted);
  flex-wrap: wrap;
}

.meta-item { display: flex; align-items: center; gap: 0.4rem; }
.meta-sep { width: 3px; height: 3px; background: var(--text-muted); border-radius: 50%; }

/* ── Article Body ─────────────────────────────────────── */
.article-body { color: var(--text); line-height: 1.8; }

.article-body section { margin-bottom: 4rem; }

.article-body h2 {
  font-size: 1.65rem;
  font-weight: 700;
  letter-spacing: -0.025em;
  color: var(--text);
  margin-top: 3.5rem;
  margin-bottom: 1.2rem;
  scroll-margin-top: 90px;
  line-height: 1.25;
}

.article-body h3 {
  font-size: 1.2rem;
  font-weight: 600;
  letter-spacing: -0.015em;
  color: var(--text);
  margin-top: 2.2rem;
  margin-bottom: 0.9rem;
  scroll-margin-top: 90px;
}

.article-body h4 {
  font-size: 1rem;
  font-weight: 600;
  color: var(--text-dim);
  margin-top: 1.5rem;
  margin-bottom: 0.6rem;
}

.article-body p { margin-bottom: 1.2rem; }
.article-body p:last-child { margin-bottom: 0; }

.article-body strong { color: var(--text); font-weight: 600; }
.article-body em { color: var(--text-dim); font-style: italic; }

.article-body a {
  color: var(--purple);
  text-decoration: underline;
  text-underline-offset: 3px;
  text-decoration-color: rgba(139,92,246,0.4);
  transition: color var(--transition), text-decoration-color var(--transition);
}
.article-body a:hover {
  color: #a78bfa;
  text-decoration-color: #a78bfa;
}

.article-body ul, .article-body ol {
  padding-left: 1.6rem;
  margin-bottom: 1.2rem;
}

.article-body li { margin-bottom: 0.4rem; }

.article-body li::marker { color: var(--purple); }

/* ── Inline code ──────────────────────────────────────── */
.article-body :not(pre) > code {
  font-family: var(--font-mono);
  font-size: 0.85em;
  background: rgba(139,92,246,0.1);
  color: var(--purple);
  border: 1px solid rgba(139,92,246,0.2);
  padding: 0.1em 0.4em;
  border-radius: 4px;
}

/* ── Code Blocks ──────────────────────────────────────── */
.code-block {
  position: relative;
  margin: 1.8rem 0;
  border-radius: var(--radius);
  border: 1px solid var(--border);
  overflow: hidden;
  background: var(--bg-code);
}

.code-block-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0.65rem 1.2rem;
  background: rgba(255,255,255,0.02);
  border-bottom: 1px solid var(--border);
}

.code-lang {
  font-size: 0.72rem;
  font-weight: 500;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--text-muted);
  font-family: var(--font-mono);
}

.copy-btn {
  font-size: 0.72rem;
  font-weight: 500;
  color: var(--text-muted);
  background: none;
  border: 1px solid var(--border);
  padding: 0.2rem 0.65rem;
  border-radius: 20px;
  transition: color var(--transition), border-color var(--transition);
}
.copy-btn:hover { color: var(--text); border-color: var(--border-hover); }

.code-block pre {
  margin: 0;
  padding: 1.4rem 1.4rem 1.4rem;
  overflow-x: auto;
  font-size: 0.875rem;
  line-height: 1.65;
  scrollbar-width: thin;
  scrollbar-color: var(--border) transparent;
}

.code-block pre::-webkit-scrollbar { height: 4px; }
.code-block pre::-webkit-scrollbar-track { background: transparent; }
.code-block pre::-webkit-scrollbar-thumb { background: var(--border); border-radius: 4px; }

/* Override Prism dark theme background */
.code-block .token.comment { color: #6b6b88; }
.code-block .token.keyword { color: #c084fc; }
.code-block .token.string  { color: #86efac; }
.code-block .token.number  { color: #fbbf24; }
.code-block .token.function{ color: #60a5fa; }
.code-block .token.operator{ color: #f472b6; }
.code-block .token.punctuation { color: #7878a0; }
.code-block .token.class-name { color: #34d399; }
.code-block .token.builtin { color: #38bdf8; }
.code-block .token.decorator { color: #fb923c; }

/* ── Callout Boxes ────────────────────────────────────── */
.callout {
  border-radius: var(--radius);
  padding: 1.2rem 1.4rem;
  margin: 1.8rem 0;
  border: 1px solid;
  font-size: 0.9rem;
  line-height: 1.7;
}

.callout-header {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  font-weight: 600;
  font-size: 0.82rem;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  margin-bottom: 0.6rem;
}

.callout.info {
  background: rgba(59,130,246,0.07);
  border-color: rgba(59,130,246,0.25);
  color: var(--text-dim);
}
.callout.info .callout-header { color: var(--blue); }

.callout.insight {
  background: rgba(139,92,246,0.08);
  border-color: rgba(139,92,246,0.25);
  color: var(--text-dim);
}
.callout.insight .callout-header { color: var(--purple); }

.callout.math {
  background: rgba(16,185,129,0.07);
  border-color: rgba(16,185,129,0.25);
  color: var(--text-dim);
  font-family: var(--font-mono);
  font-size: 0.85rem;
}
.callout.math .callout-header { color: var(--green); font-family: var(--font); }

/* ── Math display ─────────────────────────────────────── */
.math-block {
  background: var(--bg-code);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 1.2rem 1.6rem;
  margin: 1.5rem 0;
  font-family: var(--font-mono);
  font-size: 0.9rem;
  color: #a5f3fc;
  overflow-x: auto;
  line-height: 2;
  text-align: center;
}

/* ── Visualization Containers ─────────────────────────── */
.viz-wrap {
  margin: 2.5rem 0;
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  overflow: hidden;
  background: var(--bg-viz);
}

.viz-header {
  padding: 1rem 1.4rem;
  border-bottom: 1px solid var(--border);
  display: flex;
  align-items: center;
  justify-content: space-between;
  background: rgba(255,255,255,0.01);
}

.viz-title {
  font-size: 0.8rem;
  font-weight: 600;
  color: var(--text-dim);
  text-transform: uppercase;
  letter-spacing: 0.08em;
}

.viz-tag {
  font-size: 0.68rem;
  color: var(--purple);
  background: rgba(139,92,246,0.1);
  border: 1px solid rgba(139,92,246,0.25);
  padding: 0.15rem 0.55rem;
  border-radius: 20px;
  font-weight: 500;
  text-transform: uppercase;
  letter-spacing: 0.06em;
}

.viz-body { padding: 1.5rem; }

.viz-controls {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  flex-wrap: wrap;
  margin-bottom: 1.2rem;
}

.viz-btn {
  font-size: 0.8rem;
  font-weight: 500;
  color: var(--text-dim);
  background: rgba(255,255,255,0.05);
  border: 1px solid var(--border);
  padding: 0.45rem 1rem;
  border-radius: var(--radius);
  transition: all var(--transition);
}

.viz-btn:hover {
  background: rgba(255,255,255,0.1);
  color: var(--text);
  border-color: var(--border-hover);
}

.viz-btn:disabled {
  opacity: 0.35;
  cursor: not-allowed;
}

.viz-btn.primary {
  background: rgba(139,92,246,0.2);
  border-color: rgba(139,92,246,0.4);
  color: var(--purple);
}
.viz-btn.primary:hover {
  background: rgba(139,92,246,0.3);
  color: #a78bfa;
}

.viz-status {
  font-size: 0.78rem;
  color: var(--text-muted);
  font-family: var(--font-mono);
}

/* ── Tables ───────────────────────────────────────────── */
.data-table {
  width: 100%;
  border-collapse: collapse;
  font-size: 0.875rem;
  margin: 1.5rem 0;
}

.data-table th {
  text-align: left;
  padding: 0.7rem 1rem;
  background: rgba(255,255,255,0.03);
  border: 1px solid var(--border);
  font-size: 0.72rem;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--text-muted);
  font-weight: 600;
}

.data-table td {
  padding: 0.7rem 1rem;
  border: 1px solid var(--border);
  color: var(--text-dim);
  vertical-align: top;
}

.data-table tr:hover td { background: rgba(255,255,255,0.02); }

.data-table code {
  font-family: var(--font-mono);
  font-size: 0.82em;
  color: var(--purple);
}

/* ── Section Divider ──────────────────────────────────── */
.section-divider {
  border: none;
  border-top: 1px solid var(--border);
  margin: 3.5rem 0;
}

/* ── Responsive ───────────────────────────────────────── */
@media (max-width: 1100px) {
  .article-layout {
    grid-template-columns: 1fr;
  }

  .toc-sidebar {
    display: none;
  }

  .article-main {
    padding: 2.5rem 2rem 5rem;
    max-width: 100%;
  }
}

@media (max-width: 768px) {
  .hero { padding: 8rem 1.5rem 5rem; }
  .hero-title { font-size: 2rem; }
  .hero-stats { gap: 1.2rem; }
  .articles-grid { grid-template-columns: 1fr; }

  .article-main { padding: 2rem 1.2rem 4rem; }
  .article-title { font-size: 1.8rem; }
}

/* ── Scroll-reveal animations ─────────────────────────── */
.reveal {
  opacity: 0;
  transform: translateY(20px);
  transition: opacity 0.5s ease, transform 0.5s ease;
}

.reveal.visible {
  opacity: 1;
  transform: none;
}

/* ── Token Display ────────────────────────────────────── */
.token-display {
  display: flex;
  flex-wrap: wrap;
  gap: 5px;
  font-family: var(--font-mono);
  font-size: 0.85rem;
  line-height: 2.2;
  padding: 1rem;
  background: var(--bg-code);
  border-radius: var(--radius);
  min-height: 60px;
}

.tok {
  display: inline-flex;
  align-items: center;
  padding: 2px 8px;
  border-radius: 4px;
  font-size: 0.8rem;
  border: 1px solid;
  white-space: pre;
}

.tok-0  { background: rgba(139,92,246,0.15); border-color: rgba(139,92,246,0.3); color: #c4b5fd; }
.tok-1  { background: rgba(59,130,246,0.15); border-color: rgba(59,130,246,0.3); color: #93c5fd; }
.tok-2  { background: rgba(16,185,129,0.15); border-color: rgba(16,185,129,0.3); color: #6ee7b7; }
.tok-3  { background: rgba(245,158,11,0.15); border-color: rgba(245,158,11,0.3); color: #fcd34d; }
.tok-4  { background: rgba(239,68,68,0.15);  border-color: rgba(239,68,68,0.3);  color: #fca5a5; }
.tok-5  { background: rgba(236,72,153,0.15); border-color: rgba(236,72,153,0.3); color: #f9a8d4; }
.tok-6  { background: rgba(6,182,212,0.15);  border-color: rgba(6,182,212,0.3);  color: #67e8f9; }
.tok-7  { background: rgba(20,184,166,0.15); border-color: rgba(20,184,166,0.3); color: #5eead4; }
.tok-8  { background: rgba(139,92,246,0.15); border-color: rgba(139,92,246,0.3); color: #c4b5fd; }
.tok-9  { background: rgba(59,130,246,0.15); border-color: rgba(59,130,246,0.3); color: #93c5fd; }
.tok-10 { background: rgba(16,185,129,0.15); border-color: rgba(16,185,129,0.3); color: #6ee7b7; }
.tok-11 { background: rgba(245,158,11,0.15); border-color: rgba(245,158,11,0.3); color: #fcd34d; }
.tok-12 { background: rgba(239,68,68,0.15);  border-color: rgba(239,68,68,0.3);  color: #fca5a5; }