/* ===== 42 Theory — Design System ===== */
/* Identical DA to Remotion videos (glassmorphism, dark, neon accents) */

:root {
  --bg-base: #050505;
  --bg-glass: rgba(255, 255, 255, 0.03);
  --bg-glass-border: rgba(255, 255, 255, 0.1);
  --bg-glass-header: rgba(255, 255, 255, 0.015);
  --bg-dark-panel: rgba(0, 0, 0, 0.2);

  --text-primary: #f8fafc;
  --text-secondary: #94a3b8;
  --text-dim: #64748b;

  --accent-blue: #3b82f6;
  --accent-purple: #8b5cf6;
  --accent-green: #10b981;
  --accent-rose: #f43f5e;
  --accent-amber: #f59e0b;

  --accent-soft-blue: #60a5fa;

  --font-code: "JetBrains Mono", monospace;
  --font-ui: "Outfit", "Inter", sans-serif;

  --glass-blur: blur(24px);
  --glass-radius: 24px;
  --glass-shadow:
    inset 0 1px 1px rgba(255,255,255,0.15),
    inset 0 0 0 1px rgba(255,255,255,0.06),
    0 30px 60px -15px rgba(20, 20, 50, 0.5),
    0 20px 40px -20px rgba(59, 130, 246, 0.2);
}

/* ===== Reset ===== */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }
html { scroll-behavior: smooth; }
body {
  font-family: var(--font-ui);
  background: var(--bg-base);
  color: var(--text-primary);
  line-height: 1.7;
  min-height: 100vh;
  width: 100%;
}
html {
  overflow-x: clip;
}
a { color: var(--accent-blue); text-decoration: none; transition: color 0.2s; }
a:hover { color: #60a5fa; }

/* ===== Background layers (fixed) ===== */
.bg-image {
  position: fixed; inset: 0; z-index: 0;
  background: url('../img/bg42.png') center/cover no-repeat;
  filter: blur(40px) brightness(0.2) grayscale(0.6);
}
.bg-glow {
  position: fixed; inset: 0; z-index: 0;
  background:
    radial-gradient(circle at 15% 50%, rgba(96,165,250,0.15), transparent 40%),
    radial-gradient(circle at 85% 30%, rgba(96,165,250,0.08), transparent 40%);
  filter: blur(80px);
  animation: breathe 8s ease-in-out infinite alternate;
}
@keyframes breathe {
  from { transform: scale(1); }
  to { transform: scale(1.08); }
}
.bg-grid {
  position: fixed; inset: 0; z-index: 1; pointer-events: none;
  background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='56' height='100' viewBox='0 0 56 100'%3E%3Cpath d='M28 66L0 50L0 16L28 0L56 16L56 50L28 66Z' fill='none' stroke='rgba(255,255,255,0.03)' stroke-width='1'/%3E%3Cpath d='M28 100L0 84L0 50L28 34L56 50L56 84L28 100Z' fill='none' stroke='rgba(255,255,255,0.03)' stroke-width='1'/%3E%3C/svg%3E");
  background-size: 56px 68px;
  mask-image: radial-gradient(circle at center, black 40%, transparent 80%);
  -webkit-mask-image: radial-gradient(circle at center, black 40%, transparent 80%);
}
#bgc {
  position: fixed; inset: 0; z-index: 0; pointer-events: none;
  mask-image: radial-gradient(ellipse 72% 60% at 50% 44%, transparent 38%, rgba(0,0,0,.25) 55%, black 78%);
  -webkit-mask-image: radial-gradient(ellipse 72% 60% at 50% 44%, transparent 38%, rgba(0,0,0,.25) 55%, black 78%);
}

.bg-grain {
  position: fixed; inset: 0; z-index: 100; pointer-events: none;
  background-image: url('data:image/svg+xml,%3Csvg viewBox="0 0 200 200" xmlns="http://www.w3.org/2000/svg"%3E%3Cfilter id="n"%3E%3CfeTurbulence type="fractalNoise" baseFrequency="0.8" numOctaves="3" stitchTiles="stitch"/%3E%3C/filter%3E%3Crect width="100%25" height="100%25" filter="url(%23n)"/%3E%3C/svg%3E');
  opacity: 0.04;
  mix-blend-mode: overlay;
}

/* ===== Nav ===== */
.main-nav {
  position: fixed; top: 0; left: 0; right: 0; z-index: 50;
  background: rgba(5, 5, 5, 0.8);
  backdrop-filter: blur(20px);
  -webkit-backdrop-filter: blur(20px);
  border-bottom: 1px solid var(--bg-glass-border);
}
.nav-inner {
  max-width: 1200px; margin: 0 auto;
  display: flex; align-items: center; justify-content: space-between;
  padding: 14px 24px;
}
.nav-logo {
  display: flex; align-items: center; gap: 10px;
  font-weight: 700; font-size: 18px; color: var(--text-primary);
}
.nav-logo img { opacity: 0.8; }
.nav-links { display: flex; gap: 28px; font-size: 14px; font-weight: 500; }
.nav-links a { color: var(--text-secondary); }
.nav-links a:hover { color: var(--text-primary); }
.nav-links a.active {
  color: var(--text-primary);
  position: relative;
}
.nav-links a.active::after {
  content: '';
  position: absolute; bottom: -4px; left: 0; right: 0;
  height: 2px;
  background: var(--accent-soft-blue);
  border-radius: 2px;
}
.lang-dropdown { position: relative; }
.lang-dropdown .lang-switch {
  font-size: 11px; font-weight: 700; letter-spacing: 0.05em;
  padding: 4px 10px; border-radius: 6px;
  border: 1px solid rgba(255,255,255,0.15);
  color: var(--text-secondary);
  background: none; cursor: pointer;
  transition: all 0.2s;
  font-family: var(--font-ui);
}
.lang-dropdown .lang-switch:hover { color: var(--text-primary); border-color: rgba(255,255,255,0.3); }
.lang-menu {
  display: none; flex-direction: column; gap: 0;
  position: absolute; top: calc(100% + 8px); right: 0;
  background: rgba(10,10,15,0.95);
  border: 1px solid rgba(255,255,255,0.1);
  border-radius: 10px;
  padding: 6px 0;
  min-width: 120px;
  backdrop-filter: blur(20px); -webkit-backdrop-filter: blur(20px);
  box-shadow: 0 12px 32px rgba(0,0,0,0.4);
  z-index: 100;
}
.lang-dropdown.open .lang-menu { display: flex; }
.lang-menu a {
  display: block !important; padding: 8px 16px;
  font-size: 13px; font-weight: 500;
  color: var(--text-secondary);
  transition: all 0.15s;
  white-space: nowrap;
}
.lang-menu a:hover { color: var(--text-primary); background: rgba(255,255,255,0.05); }
.nav-toggle { display: none; background: none; border: none; color: var(--text-primary); font-size: 22px; cursor: pointer; }

@keyframes pageFadeIn {
  from { opacity: 0; transform: translateY(10px); }
  to   { opacity: 1; transform: none; }
}

/* ===== Main content ===== */
.main-content {
  position: relative; z-index: 2;
  max-width: 1200px; margin: 0 auto;
  padding: 100px 24px 60px;
  width: 100%;
  box-sizing: border-box;
  animation: pageFadeIn 0.3s ease-out both;
}

/* ===== Glass Panel ===== */
.glass-panel {
  background: var(--bg-glass);
  backdrop-filter: var(--glass-blur);
  -webkit-backdrop-filter: var(--glass-blur);
  border-radius: var(--glass-radius);
  box-shadow: var(--glass-shadow);
  border: none;
  overflow: hidden;
}
.glass-header {
  padding: 16px 24px;
  border-bottom: 1px solid var(--bg-glass-border);
  background: var(--bg-glass-header);
  display: flex; align-items: center; gap: 12px;
}

/* ===== Hero (lesson page) ===== */
.lesson-hero {
  text-align: center;
  padding: 60px 20px 40px;
}
.lesson-hero .lesson-id {
  font-size: 14px; font-weight: 600; color: var(--lesson-color, var(--accent-soft-blue));
  text-transform: uppercase; letter-spacing: 3px; margin-bottom: 12px;
}
.lesson-hero h1 {
  font-size: 48px; font-weight: 800;
  background: linear-gradient(90deg, var(--lesson-color, #61afef), color-mix(in srgb, var(--lesson-color, #56b6c2) 55%, white));
  -webkit-background-clip: text; -webkit-text-fill-color: transparent;
  filter: drop-shadow(0 0 20px color-mix(in srgb, var(--lesson-color, #56b6c2) 35%, transparent));
  margin-bottom: 16px;
}
.lesson-hero .lesson-desc {
  font-size: 18px; color: var(--text-secondary); max-width: 600px; margin: 0 auto;
}
.lesson-prereqs {
  display: flex; gap: 8px; justify-content: center; margin-top: 20px; flex-wrap: wrap;
}
.lesson-prereqs a {
  font-size: 12px; padding: 4px 12px; border-radius: 20px;
  background: color-mix(in srgb, var(--prereq-color, var(--accent-blue)) 12%, transparent);
  border: 1px solid color-mix(in srgb, var(--prereq-color, var(--accent-blue)) 30%, transparent);
  color: var(--prereq-color, var(--accent-blue)); font-weight: 600;
  transition: all 0.2s;
}
.lesson-prereqs a:hover {
  background: color-mix(in srgb, var(--prereq-color, var(--accent-blue)) 20%, transparent);
  border-color: color-mix(in srgb, var(--prereq-color, var(--accent-blue)) 55%, transparent);
  box-shadow: 0 0 14px color-mix(in srgb, var(--prereq-color, var(--accent-blue)) 30%, transparent);
  transform: translateY(-1px);
}

/* ===== Lesson layout ===== */
.lesson-layout {
  display: grid;
  grid-template-columns: 220px 1fr;
  gap: 40px;
  align-items: start;
  min-width: 0;
}
.lesson-toc {
  position: sticky;
  top: 90px;
  max-height: calc(100vh - 120px);
  overflow-y: auto;
  align-self: start;
}
.lesson-toc h3 {
  font-size: 11px; font-weight: 600; color: var(--text-dim);
  text-transform: uppercase; letter-spacing: 2px; margin-bottom: 16px;
}
.lesson-toc a {
  display: block; padding: 6px 10px 6px 12px; font-size: 13px;
  color: var(--text-secondary); border-left: 2px solid transparent;
  transition: all 0.2s; border-radius: 0 8px 8px 0;
}
.lesson-toc a:hover {
  color: var(--text-primary); border-left-color: var(--lesson-color, var(--accent-soft-blue));
  background: color-mix(in srgb, var(--lesson-color, var(--accent-soft-blue)) 6%, transparent);
}
.lesson-toc a.active {
  color: var(--text-primary); border-left-color: var(--lesson-color, var(--accent-soft-blue));
  background: color-mix(in srgb, var(--lesson-color, var(--accent-soft-blue)) 12%, transparent);
}

/* ===== Lesson body ===== */
.lesson-body {
  min-width: 0;
  overflow-wrap: break-word;
  word-wrap: break-word;
  max-width: 720px;
}
.lesson-body h2 {
  font-size: 28px; font-weight: 700; margin: 48px 0 20px;
  border-left: 3px solid var(--lesson-color, var(--accent-soft-blue));
  padding-left: 14px;
}
.lesson-body h3 {
  font-size: 20px; font-weight: 600; margin: 32px 0 12px; color: var(--text-primary);
}
.lesson-body p {
  margin-bottom: 16px; color: var(--text-secondary); font-size: 16px; line-height: 1.8;
}
.lesson-body strong { color: var(--text-primary); }
.lesson-body ol li, .lesson-body ul li {
  margin-bottom: 12px;
}
.lesson-body code {
  font-family: var(--font-code); font-size: 14px;
  background: rgba(255,255,255,0.06); padding: 2px 8px; border-radius: 6px;
  color: #e5c07b;
  white-space: nowrap;
  display: inline-block;
  max-width: 100%;
  overflow-x: auto;
  vertical-align: bottom;
  letter-spacing: 0.5px;
  font-variant-ligatures: none;
  font-feature-settings: "liga" 0, "calt" 0;
}

/* ===== Tables ===== */
.table-wrap {
  margin: 20px 0; overflow-x: auto;
}
.table-wrap table {
  width: 100%; border-collapse: collapse;
  font-size: 14px;
}
.table-wrap th {
  text-align: left; padding: 10px 16px;
  background: var(--bg-dark-panel);
  color: var(--text-primary); font-weight: 600;
  border-bottom: 1px solid var(--bg-glass-border);
  font-size: 13px; text-transform: uppercase; letter-spacing: 0.5px;
}
.table-wrap td {
  padding: 10px 16px;
  border-bottom: 1px solid rgba(255,255,255,0.04);
  color: var(--text-secondary);
}
.table-wrap tr:hover td {
  background: rgba(255,255,255,0.02);
}
.table-wrap code {
  font-size: 13px;
}

/* ===== Info cards ===== */
.info-card {
  display: flex; gap: 0; margin: 20px 0; border-radius: 12px;
  background: var(--bg-dark-panel);
  border: 1px solid color-mix(in srgb, var(--card-color) 20%, transparent);
  overflow: hidden;
}
.info-bar {
  width: 4px; flex-shrink: 0;
  background: var(--card-color);
  box-shadow: 0 0 12px color-mix(in srgb, var(--card-color) 40%, transparent);
}
.info-content {
  padding: 16px 20px; font-size: 15px; color: var(--text-secondary); line-height: 1.6;
}
.info-icon { margin-right: 6px; }

/* ===== Concept list (cards grid) ===== */
.concept-list {
  display: flex; flex-wrap: wrap; gap: 16px; margin: 24px 0;
}
.concept-card {
  flex: 1 1 300px;
  background: var(--bg-dark-panel);
  border-radius: 16px;
  padding: 20px 24px;
  display: flex; align-items: center; gap: 18px;
  border: 1px solid rgba(255,255,255,0.05);
}
.concept-card .accent-bar {
  width: 4px; height: 44px; border-radius: 4px; flex-shrink: 0;
}
.concept-card .card-label {
  font-family: var(--font-ui); font-size: 18px; font-weight: 700;
}
.concept-card .card-desc {
  font-family: var(--font-code); font-size: 14px; color: rgba(255,255,255,0.55);
  margin-top: 4px;
}

/* ===== Video embed ===== */
.video-embed {
  margin: 30px 0; border-radius: 16px; overflow: hidden;
  aspect-ratio: 16 / 9;
}
.video-embed iframe {
  width: 100%; height: 100%; border: none;
}

/* ===== Lesson nav (prev/next) ===== */
.lesson-nav {
  display: flex; justify-content: space-between; margin-top: 60px;
  padding-top: 30px; border-top: 1px solid var(--bg-glass-border);
}
.lesson-nav a {
  display: flex; flex-direction: column; gap: 4px;
  padding: 16px 24px; border-radius: 16px;
  background: var(--bg-dark-panel); border: 1px solid var(--bg-glass-border);
  transition: all 0.2s; max-width: 45%;
}
.lesson-nav a:hover {
  border-color: var(--accent-blue);
  box-shadow: 0 0 20px rgba(59,130,246,0.1);
}
.lesson-nav .nav-label {
  font-size: 12px; color: var(--text-dim); text-transform: uppercase; letter-spacing: 1px;
}
.lesson-nav .nav-title {
  font-size: 16px; font-weight: 600; color: var(--text-primary);
}

/* ===== Landing: Cards grid ===== */
.hero-section {
  text-align: center; padding: 80px 0 60px;
}
.hero-section h1 {
  font-size: 64px; font-weight: 800;
  background: linear-gradient(90deg, var(--accent-soft-blue), color-mix(in srgb, var(--accent-soft-blue) 60%, white));
  -webkit-background-clip: text; -webkit-text-fill-color: transparent;
  filter: drop-shadow(0 0 30px rgba(130,170,255,0.4));
}
.hero-section p {
  font-size: 20px; color: var(--text-secondary); margin-top: 16px;
}

.section-title {
  font-size: 13px; font-weight: 600; color: var(--text-dim);
  text-transform: uppercase; letter-spacing: 2px;
  margin: 48px 0 20px;
  display: flex; align-items: center; gap: 12px;
}
.section-title::after {
  content: ''; flex: 1; height: 1px; background: var(--bg-glass-border);
}

.cards-grid {
  display: grid; grid-template-columns: repeat(auto-fill, minmax(320px, 1fr));
  gap: 16px;
}
.lesson-card {
  display: flex; align-items: stretch; gap: 0;
  border-radius: 16px;
  cursor: pointer;
  background: var(--bg-dark-panel);
  border: 1px solid rgba(255,255,255,0.05);
  transition: border-color .25s ease-out, box-shadow .25s ease-out, transform .25s ease-out, opacity .45s ease-out;
  overflow: hidden;
}
.lesson-card[data-reveal],
.th-row[data-reveal],
.th-tronc-card[data-reveal],
.th-section-hd-inner[data-reveal] {
  opacity: 0;
  transform: translateX(48px);
}
.lesson-card[data-reveal].revealed,
.th-row[data-reveal].revealed,
.th-tronc-card[data-reveal].revealed,
.th-section-hd-inner[data-reveal].revealed {
  opacity: 1;
  transform: translateX(0);
  transition: opacity .55s cubic-bezier(0.16,1,0.3,1), transform .55s cubic-bezier(0.16,1,0.3,1) !important;
}
.lesson-card:hover {
  border-color: var(--card-color);
  box-shadow: 0 0 25px color-mix(in srgb, var(--card-color) 20%, transparent);
  transform: translateY(-3px);
  transition: border-color .25s ease-out, box-shadow .25s ease-out, transform .25s ease-out;
}
.lesson-card:active {
  transform: translateY(-1px);
  transition-duration: .1s;
}
.lesson-card .card-accent {
  width: 4px; flex-shrink: 0;
}
.lesson-card .card-info {
  padding: 20px 24px;
}
.lesson-card .card-info .card-title {
  font-size: 16px; font-weight: 600; color: var(--text-primary);
}
.lesson-card .card-info .card-section {
  font-size: 12px; color: var(--text-dim); margin-top: 2px;
}

/* ===== Quiz ===== */
.quiz {
  margin: 48px 0;
}
.quiz-header h2 {
  border-bottom: none; margin-bottom: 8px;
}
.quiz-subtitle {
  color: var(--text-dim); font-size: 14px; margin-bottom: 32px;
}
.quiz-question {
  background: var(--bg-dark-panel);
  border: 1px solid var(--bg-glass-border);
  border-radius: 16px;
  padding: 24px;
  margin-bottom: 16px;
  transition: border-color 0.3s;
}
.quiz-question.correct { border-color: var(--accent-green); }
.quiz-question.wrong { border-color: var(--accent-rose); }

.quiz-q-header {
  display: flex; align-items: flex-start; gap: 14px; margin-bottom: 16px;
}
.quiz-num {
  font-family: var(--font-code); font-size: 14px; font-weight: 700;
  width: 32px; height: 32px; border-radius: 10px;
  display: flex; align-items: center; justify-content: center;
  background: rgba(59,130,246,0.1); color: var(--accent-blue);
  flex-shrink: 0;
}
.quiz-q-text {
  font-size: 16px; font-weight: 500; color: var(--text-primary); line-height: 1.5;
}
.quiz-code {
  display: block;
  background: var(--bg-dark-panel);
  border: 1px solid var(--bg-glass-border);
  border-radius: 10px;
  padding: 12px 16px;
  margin: 10px 0;
  font-family: var(--font-code);
  font-size: 13px;
  line-height: 1.6;
  white-space: pre;
  overflow-x: auto;
  font-variant-ligatures: none;
  font-feature-settings: "liga" 0, "calt" 0;
}
.quiz-code code {
  background: none;
  padding: 0;
  font-size: inherit;
  color: var(--text-secondary);
  display: inline;
  white-space: pre;
}
.quiz-choices {
  display: flex; flex-direction: column; gap: 8px;
}
.quiz-choice {
  display: block; width: 100%; text-align: left;
  padding: 12px 18px; border-radius: 12px;
  background: rgba(255,255,255,0.03);
  border: 1px solid rgba(255,255,255,0.08);
  color: var(--text-secondary);
  font-family: var(--font-ui); font-size: 15px;
  cursor: pointer; transition: all 0.2s;
}
.quiz-choice:hover:not(.selected):not(.disabled) {
  border-color: var(--accent-blue);
  color: var(--text-primary);
  background: rgba(59,130,246,0.05);
}
.quiz-choice.selected {
  border-color: var(--accent-blue);
  background: rgba(59,130,246,0.1);
  color: var(--text-primary);
  font-weight: 600;
}
.quiz-choice:active:not(.disabled) {
  transform: scale(0.98);
}
.quiz-choice.correct-answer {
  border-color: var(--accent-green);
  background: rgba(16,185,129,0.1);
  animation: selectPop 0.25s ease-out;
  color: var(--accent-green);
  font-weight: 600;
}
.quiz-choice.wrong-answer {
  border-color: var(--accent-rose);
  background: rgba(244,63,94,0.1);
  animation: shake 0.35s ease-out;
  color: var(--accent-rose);
  opacity: 0.7;
}
.quiz-choice.disabled { cursor: default; pointer-events: none; }

.quiz-explain {
  margin-top: 12px; padding: 14px 18px;
  border-radius: 10px;
  background: rgba(255,255,255,0.02);
  border-left: 3px solid var(--accent-blue);
}
.quiz-explain p {
  font-size: 14px; color: var(--text-secondary); margin: 0; line-height: 1.6;
}

.quiz-result {
  margin-top: 24px; padding: 24px 28px;
  border-radius: 16px; text-align: center;
  font-size: 22px; font-weight: 700;
  letter-spacing: .02em;
}
.quiz-result.good {
  background: linear-gradient(135deg, rgba(16,185,129,0.15), rgba(16,185,129,0.05));
  border: 1px solid rgba(16,185,129,0.35);
  color: var(--accent-green);
  box-shadow: 0 0 32px rgba(16,185,129,0.12), inset 0 1px 0 rgba(16,185,129,0.15);
}
.quiz-result.mid {
  background: linear-gradient(135deg, rgba(100,116,139,0.15), rgba(100,116,139,0.05));
  border: 1px solid rgba(100,116,139,0.35);
  color: #94a3b8;
  box-shadow: 0 0 32px rgba(100,116,139,0.08), inset 0 1px 0 rgba(100,116,139,0.15);
}
.quiz-result.bad {
  background: linear-gradient(135deg, rgba(244,63,94,0.15), rgba(244,63,94,0.05));
  border: 1px solid rgba(244,63,94,0.35);
  color: var(--accent-rose);
  box-shadow: 0 0 32px rgba(244,63,94,0.12), inset 0 1px 0 rgba(244,63,94,0.15);
}

/* ===== Reading Progress Bar ===== */
#reading-progress {
  position: fixed; top: 0; left: 0; z-index: 200;
  height: 2px; width: 0%;
  background: linear-gradient(90deg, var(--lesson-color, var(--accent-blue)), color-mix(in srgb, var(--lesson-color, var(--accent-blue)) 55%, white));
  box-shadow: 0 0 8px color-mix(in srgb, var(--lesson-color, var(--accent-blue)) 60%, transparent);
  transition: width 0.1s linear;
  pointer-events: none;
}
/* ===== Quiz micro-animations ===== */
@keyframes selectPop {
  0%   { transform: scale(1); }
  45%  { transform: scale(1.025); }
  100% { transform: scale(1); }
}
@keyframes shake {
  0%, 100% { transform: translateX(0); }
  20%       { transform: translateX(-6px); }
  40%       { transform: translateX(6px); }
  60%       { transform: translateX(-4px); }
  80%       { transform: translateX(4px); }
}

@media (prefers-reduced-motion: reduce) {
  #reading-progress { transition: none; }
  .bg-glow { animation: none; }
  #terminal { animation: none; }
  .rm-course { opacity: 1; transform: none; transition: none; }
  .rm-course-card { transition: none; }
  .rm-course-dot { transition: none; }
  .quiz-choice { transition: none; }
  .lesson-card { animation: none; opacity: 1; transition: none; }
  * { animation-duration: 0.01ms !important; transition-duration: 0.01ms !important; }
}

/* ===== Focus States (WCAG 2.1 AA) ===== */
:focus-visible {
  outline: 2px solid var(--accent-blue);
  outline-offset: 3px;
  border-radius: 4px;
}
.rm-course:focus-visible .rm-course-card {
  outline: 2px solid var(--accent-blue);
  outline-offset: 2px;
  border-radius: 14px;
}
.quiz-choice:focus-visible {
  outline: 2px solid var(--accent-blue);
  outline-offset: 2px;
}
:focus:not(:focus-visible) { outline: none; }

/* ===== Skip link (a11y) ===== */
.skip-link {
  position: absolute; top: -100px; left: 16px; z-index: 9999;
  padding: 10px 20px; border-radius: 8px;
  background: var(--accent-blue); color: #fff;
  font-family: var(--font-ui); font-size: 14px; font-weight: 600;
  transition: top 0.2s;
  text-decoration: none;
}
.skip-link:focus { top: 16px; }

/* ===== TOC toggle (mobile) ===== */
.toc-toggle {
  display: none;
  align-items: center; gap: 8px;
  width: 100%; margin-bottom: 8px;
  padding: 10px 16px;
  font-family: var(--font-ui); font-size: 13px; font-weight: 600;
  color: var(--text-secondary);
  background: var(--bg-dark-panel);
  border: 1px solid var(--bg-glass-border);
  border-radius: 12px;
  cursor: pointer;
  transition: color .2s, border-color .2s;
}
.toc-toggle:hover { color: var(--text-primary); border-color: var(--accent-blue); }
.toc-toggle svg { flex-shrink: 0; }

/* ===== Footer ===== */
.main-footer {
  position: relative; z-index: 2;
  border-top: 1px solid var(--bg-glass-border);
  padding: 30px 24px; margin-top: 80px;
}
.footer-inner {
  max-width: 1200px; margin: 0 auto;
  display: flex; justify-content: space-between; align-items: center;
}
.footer-links { display: flex; gap: 24px; }
.footer-links a { color: var(--text-dim); font-size: 13px; }
.footer-links a:hover { color: var(--text-secondary); }
.footer-copy { color: var(--text-dim); font-size: 13px; }