/* =========================================================
   Variable Compleja — Estilo Principal
   Prof. Mariano Miguel Lanzi
   Basado en el diseño de Mecánica Lagrangiana
   ========================================================= */

:root {
  --bg-main: #0d1117;
  --bg-sidebar: #161b22;
  --bg-card: #1c2333;
  --bg-input: #21262d;
  --text-primary: #e6edf3;
  --text-secondary: #8b949e;
  --text-muted: #6e7681;
  --accent: #c7256c;
  --accent-hover: #e0528a;
  --accent-gold: #d4a72c;
  --accent-green: #3fb950;
  --accent-red: #f85149;
  --accent-purple: #a371f7;
  --border: #30363d;
  --border-light: #21262d;
  --shadow: 0 2px 8px rgba(0,0,0,0.3);
  --radius: 8px;
  --transition: 0.2s ease;
  --font-mono: 'JetBrains Mono', 'Fira Code', 'Consolas', monospace;
  --font-sans: 'Inter', 'Segoe UI', system-ui, -apple-system, sans-serif;
  --sidebar-width: 260px;
}

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

html {
  scroll-behavior: smooth;
  font-size: 16px;
}

body {
  font-family: var(--font-sans);
  background: var(--bg-main);
  color: var(--text-primary);
  line-height: 1.7;
  display: flex;
  min-height: 100vh;
}

a {
  color: var(--accent);
  text-decoration: none;
  transition: color var(--transition);
}
a:hover { color: var(--accent-hover); }

img { max-width: 100%; height: auto; }

code {
  font-family: var(--font-mono);
  background: var(--bg-input);
  padding: 2px 6px;
  border-radius: 4px;
  font-size: 0.9em;
}

/* ============ SIDEBAR ============ */
.sidebar {
  position: fixed;
  top: 0;
  left: 0;
  width: var(--sidebar-width);
  height: 100vh;
  background: var(--bg-sidebar);
  border-right: 1px solid var(--border);
  overflow-y: auto;
  z-index: 100;
  padding: 24px 0;
  display: flex;
  flex-direction: column;
}

.sidebar-header {
  padding: 0 20px 20px;
  border-bottom: 1px solid var(--border);
  margin-bottom: 12px;
}

.sidebar-header h2 {
  font-size: 1.1rem;
  color: var(--accent-gold);
  line-height: 1.3;
}

.sidebar-header small {
  font-size: 0.75rem;
  color: var(--text-muted);
}

.sidebar-nav {
  flex: 1;
  padding: 0 8px;
}

.sidebar-nav a {
  display: block;
  padding: 8px 16px;
  color: var(--text-secondary);
  border-radius: 6px;
  font-size: 0.875rem;
  transition: all var(--transition);
  margin-bottom: 2px;
}

.sidebar-nav a:hover,
.sidebar-nav a.active {
  background: rgba(199, 37, 108, 0.1);
  color: var(--accent);
}

.sidebar-nav a.active {
  border-left: 3px solid var(--accent);
  padding-left: 13px;
}

.sidebar-nav .nav-home {
  font-weight: 600;
  color: var(--text-primary);
  margin-bottom: 8px;
}

.sidebar-footer {
  padding: 16px 20px;
  border-top: 1px solid var(--border);
  font-size: 0.7rem;
  color: var(--text-muted);
}

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

.container {
  max-width: 900px;
  margin: 0 auto;
  padding: 40px 32px 80px;
}

/* ============ HEADER ============ */
.page-header {
  text-align: center;
  padding: 60px 0 40px;
  border-bottom: 1px solid var(--border);
  margin-bottom: 40px;
}

.page-header h1 {
  font-size: 2rem;
  color: var(--accent-gold);
  margin-bottom: 8px;
}

.page-header .subtitle {
  font-size: 1.1rem;
  color: var(--text-secondary);
}

.page-header .author {
  font-size: 0.85rem;
  color: var(--text-muted);
  margin-top: 8px;
}

/* ============ SECTIONS ============ */
.section {
  margin-bottom: 48px;
}

.section h2 {
  font-size: 1.5rem;
  color: var(--accent);
  margin-bottom: 16px;
  padding-bottom: 8px;
  border-bottom: 1px solid var(--border);
}

.section h3 {
  font-size: 1.2rem;
  color: var(--accent-hover);
  margin: 24px 0 12px;
}

.section h4 {
  font-size: 1rem;
  color: var(--text-primary);
  margin: 20px 0 8px;
}

.section p {
  margin-bottom: 14px;
  color: var(--text-secondary);
}

.section ul, .section ol {
  margin: 8px 0 14px 20px;
  color: var(--text-secondary);
}

.section li {
  margin-bottom: 6px;
}

/* ============ CARDS ============ */
.card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 20px 24px;
  margin: 20px 0;
  box-shadow: var(--shadow);
}

.card h3 {
  margin-top: 0;
  color: var(--accent-gold);
}

.card.info {
  border-left: 4px solid var(--accent);
}

.card.warning {
  border-left: 4px solid var(--accent-gold);
}

.card.success {
  border-left: 4px solid var(--accent-green);
}

/* ============ EQUATIONS ============ */
.eq-wrapper {
  background: var(--bg-input);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 16px 20px;
  margin: 16px 0;
  overflow-x: auto;
  text-align: center;
}

.eq-wrapper .MathJax {
  font-size: 1.05em !important;
}

/* ============ TABLES ============ */
table {
  width: 100%;
  border-collapse: collapse;
  margin: 16px 0;
  font-size: 0.9rem;
}

th, td {
  padding: 10px 14px;
  text-align: left;
  border: 1px solid var(--border);
}

th {
  background: var(--bg-input);
  color: var(--accent);
  font-weight: 600;
}

td {
  color: var(--text-secondary);
}

tr:nth-child(even) td {
  background: rgba(255,255,255,0.015);
}

/* ============ QUIZ ============ */
.quiz-container {
  margin: 40px 0;
}

.quiz-question {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 20px 24px;
  margin-bottom: 16px;
}

.quiz-question h4 {
  color: var(--text-primary);
  margin-bottom: 12px;
}

.quiz-options {
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.quiz-option {
  display: flex;
  align-items: center;
  gap: 10px;
  padding: 10px 14px;
  background: var(--bg-input);
  border: 1px solid var(--border-light);
  border-radius: 6px;
  cursor: pointer;
  transition: all var(--transition);
  font-size: 0.9rem;
  color: var(--text-secondary);
}

.quiz-option:hover {
  border-color: var(--accent);
  background: rgba(199, 37, 108, 0.05);
}

.quiz-option input[type="radio"] {
  accent-color: var(--accent);
  width: 16px;
  height: 16px;
}

.quiz-option.correct {
  border-color: var(--accent-green) !important;
  background: rgba(63, 185, 80, 0.1) !important;
  color: var(--accent-green) !important;
}

.quiz-option.incorrect {
  border-color: var(--accent-red) !important;
  background: rgba(248, 81, 73, 0.1) !important;
  color: var(--accent-red) !important;
}

.quiz-feedback {
  margin-top: 8px;
  font-size: 0.85rem;
  padding: 8px 12px;
  border-radius: 4px;
  display: none;
}

.quiz-feedback.show {
  display: block;
}

.quiz-feedback.correct {
  background: rgba(63, 185, 80, 0.1);
  color: var(--accent-green);
  border: 1px solid rgba(63, 185, 80, 0.3);
}

.quiz-feedback.incorrect {
  background: rgba(248, 81, 73, 0.1);
  color: var(--accent-red);
  border: 1px solid rgba(248, 81, 73, 0.3);
}

.quiz-actions {
  display: flex;
  gap: 12px;
  margin-top: 24px;
}

.btn {
  padding: 10px 20px;
  border: 1px solid var(--border);
  border-radius: 6px;
  background: var(--bg-card);
  color: var(--text-primary);
  cursor: pointer;
  font-family: var(--font-sans);
  font-size: 0.9rem;
  transition: all var(--transition);
}

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

.btn-primary {
  background: var(--accent);
  border-color: var(--accent);
  color: #fff;
  font-weight: 600;
}

.btn-primary:hover {
  background: var(--accent-hover);
  border-color: var(--accent-hover);
  color: #fff;
}

.quiz-score {
  text-align: center;
  font-size: 1.2rem;
  font-weight: 600;
  margin-top: 16px;
  padding: 12px;
  border-radius: var(--radius);
  display: none;
}

.quiz-score.show {
  display: block;
}

.quiz-score.good {
  background: rgba(63, 185, 80, 0.1);
  color: var(--accent-green);
  border: 1px solid rgba(63, 185, 80, 0.3);
}

.quiz-score.medium {
  background: rgba(212, 167, 44, 0.1);
  color: var(--accent-gold);
  border: 1px solid rgba(212, 167, 44, 0.3);
}

.quiz-score.bad {
  background: rgba(248, 81, 73, 0.1);
  color: var(--accent-red);
  border: 1px solid rgba(248, 81, 73, 0.3);
}

/* ============ CHAPTER NAVIGATION ============ */
.chapter-nav {
  display: flex;
  justify-content: space-between;
  margin-top: 48px;
  padding-top: 24px;
  border-top: 1px solid var(--border);
}

.chapter-nav a {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 8px 16px;
  border: 1px solid var(--border);
  border-radius: 6px;
  font-size: 0.85rem;
  transition: all var(--transition);
}

.chapter-nav a:hover {
  border-color: var(--accent);
  background: rgba(199, 37, 108, 0.05);
}

.chapter-nav .prev::before { content: '← '; }
.chapter-nav .next::after { content: ' →'; }

/* ============ BIBLIOGRAPHY ============ */
.bib-list {
  list-style: none;
  margin: 0;
  padding: 0;
}

.bib-list li {
  padding: 12px 16px;
  margin-bottom: 8px;
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  transition: border-color var(--transition);
}

.bib-list li:hover {
  border-color: var(--accent);
}

.bib-list .bib-title {
  font-weight: 600;
  color: var(--text-primary);
}

.bib-list .bib-author {
  color: var(--text-secondary);
  font-size: 0.9rem;
}

.bib-list .bib-detail {
  color: var(--text-muted);
  font-size: 0.8rem;
}

/* ============ CHAPTER INDEX CARDS ============ */
.chapter-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
  gap: 16px;
  margin: 24px 0;
}

.chapter-card {
  display: block;
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 20px;
  transition: all var(--transition);
}

.chapter-card:hover {
  border-color: var(--accent);
  transform: translateY(-2px);
  box-shadow: 0 4px 16px rgba(0,0,0,0.4);
}

.chapter-card .chap-num {
  font-size: 0.75rem;
  color: var(--accent);
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 1px;
}

.chapter-card h3 {
  margin: 6px 0 8px;
  font-size: 1rem;
  color: var(--text-primary);
}

.chapter-card p {
  font-size: 0.82rem;
  color: var(--text-muted);
  margin: 0;
}

/* ============ HERO / INTRO ============ */
.hero {
  text-align: center;
  padding: 60px 20px 50px;
}

.hero h1 {
  font-size: 2.4rem;
  color: var(--accent-gold);
  margin-bottom: 8px;
}

.hero .hero-subtitle {
  font-size: 1.2rem;
  color: var(--text-secondary);
  margin-bottom: 16px;
}

.hero p {
  max-width: 700px;
  margin: 0 auto 8px;
  color: var(--text-muted);
  font-size: 0.95rem;
}

/* ============ FOOTER ============ */
.page-footer {
  text-align: center;
  padding: 24px;
  border-top: 1px solid var(--border);
  color: var(--text-muted);
  font-size: 0.8rem;
  margin-top: 48px;
}

.page-footer a {
  color: var(--text-secondary);
}

/* ============ RESPONSIVE ============ */
@media (max-width: 768px) {
  .sidebar {
    position: relative;
    width: 100%;
    height: auto;
    border-right: none;
    border-bottom: 1px solid var(--border);
    padding: 16px 0;
  }

  .sidebar-nav {
    display: flex;
    flex-wrap: wrap;
    gap: 4px;
    padding: 0 12px;
  }

  .sidebar-nav a {
    font-size: 0.78rem;
    padding: 6px 10px;
  }

  body { flex-direction: column; }
  .main { margin-left: 0; }
  .container { padding: 24px 16px 60px; }

  .chapter-grid { grid-template-columns: 1fr; }
  .page-header h1 { font-size: 1.5rem; }
  .hero h1 { font-size: 1.7rem; }
  .chapter-nav { flex-direction: column; gap: 8px; }
}