/* ============================================================
   ROOT VARIABLES
   ============================================================ */
:root {
  --bg-base:      #080c14;
  --bg-surface:   #0d1424;
  --bg-card:      #0f1a2e;
  --bg-card-hover:#132035;

  --accent-cyan:  #00d4ff;
  --accent-blue:  #0075ff;
  --accent-glow:  rgba(0, 212, 255, 0.15);

  --text-primary:   #e8f0fe;
  --text-secondary: #7a93b8;
  --text-muted:     #3d5475;

  --border:       rgba(0, 212, 255, 0.12);
  --border-hover: rgba(0, 212, 255, 0.4);

  --nav-height: 64px;
  --radius:     12px;
  --transition: 0.3s ease;
}

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

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

body {
  background-color: var(--bg-base);
  color: var(--text-primary);
  font-family: 'Segoe UI', 'Helvetica Neue', Arial, sans-serif;
  line-height: 1.6;
  overflow-x: hidden;
}

a { color: inherit; text-decoration: none; }
img, svg { display: block; }

/* ============================================================
   SCROLLBAR
   ============================================================ */
::-webkit-scrollbar { width: 6px; }
::-webkit-scrollbar-track { background: var(--bg-base); }
::-webkit-scrollbar-thumb { background: var(--accent-blue); border-radius: 3px; }

/* ============================================================
   NAVBAR
   ============================================================ */
.navbar {
  position: fixed;
  top: 0; left: 0; right: 0;
  z-index: 1000;
  height: var(--nav-height);
  background: rgba(8, 12, 20, 0.85);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--border);
  transition: background var(--transition);
}

.navbar.scrolled {
  background: rgba(8, 12, 20, 0.97);
}

.nav-inner {
  max-width: 1200px;
  margin: 0 auto;
  height: 100%;
  padding: 0 24px;
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.nav-logo {
  font-size: 1.1rem;
  font-weight: 700;
  letter-spacing: 0.05em;
  color: var(--text-primary);
}

.logo-bracket {
  color: var(--accent-cyan);
}

.nav-menu {
  display: flex;
  gap: 8px;
}

.nav-link {
  padding: 6px 16px;
  border-radius: 6px;
  font-size: 0.875rem;
  font-weight: 500;
  color: var(--text-secondary);
  transition: color var(--transition), background var(--transition);
  letter-spacing: 0.03em;
}

.nav-link:hover,
.nav-link.active {
  color: var(--accent-cyan);
  background: var(--accent-glow);
}

/* Hamburger */
.nav-toggle {
  display: none;
  flex-direction: column;
  gap: 5px;
  background: none;
  border: none;
  cursor: pointer;
  padding: 4px;
}

.nav-toggle span {
  display: block;
  width: 24px;
  height: 2px;
  background: var(--text-primary);
  border-radius: 2px;
  transition: var(--transition);
}

/* ============================================================
   HERO
   ============================================================ */
.hero {
  position: relative;
  min-height: 100vh;
  display: flex;
  align-items: center;
  justify-content: center;
  overflow: hidden;
  padding-top: var(--nav-height);
}

/* Background layers */
.hero-bg {
  position: absolute;
  inset: 0;
  pointer-events: none;
}

.grid-overlay {
  position: absolute;
  inset: 0;
  background-image:
    linear-gradient(rgba(0,212,255,0.04) 1px, transparent 1px),
    linear-gradient(90deg, rgba(0,212,255,0.04) 1px, transparent 1px);
  background-size: 48px 48px;
}

.glow {
  position: absolute;
  border-radius: 50%;
  filter: blur(90px);
  opacity: 0.35;
}

.glow-1 {
  width: 600px; height: 600px;
  top: -150px; left: -100px;
  background: radial-gradient(circle, rgba(0,117,255,0.5), transparent 70%);
  animation: glowPulse 6s ease-in-out infinite alternate;
}

.glow-2 {
  width: 500px; height: 500px;
  bottom: -100px; right: -80px;
  background: radial-gradient(circle, rgba(0,212,255,0.4), transparent 70%);
  animation: glowPulse 8s ease-in-out infinite alternate-reverse;
}

@keyframes glowPulse {
  from { opacity: 0.25; transform: scale(1); }
  to   { opacity: 0.45; transform: scale(1.1); }
}

/* Hero content */
.hero-content {
  position: relative;
  text-align: center;
  padding: 0 24px;
  max-width: 800px;
}

.hero-tag {
  font-size: 0.85rem;
  letter-spacing: 0.15em;
  color: var(--accent-cyan);
  margin-bottom: 20px;
  font-family: 'Courier New', monospace;
}

.hero-title {
  font-size: clamp(2.4rem, 6vw, 4.5rem);
  font-weight: 800;
  line-height: 1.15;
  letter-spacing: -0.02em;
  margin-bottom: 24px;
  color: var(--text-primary);
}

.hero-accent {
  background: linear-gradient(90deg, var(--accent-cyan), var(--accent-blue));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.hero-desc {
  font-size: 1.05rem;
  color: var(--text-secondary);
  line-height: 1.8;
  margin-bottom: 40px;
}

.hero-btns {
  display: flex;
  gap: 16px;
  justify-content: center;
  flex-wrap: wrap;
}

.btn {
  display: inline-block;
  padding: 12px 32px;
  border-radius: 8px;
  font-size: 0.95rem;
  font-weight: 600;
  letter-spacing: 0.04em;
  transition: all var(--transition);
  cursor: pointer;
}

.btn-primary {
  background: linear-gradient(135deg, var(--accent-blue), var(--accent-cyan));
  color: #fff;
  box-shadow: 0 0 24px rgba(0, 117, 255, 0.35);
}

.btn-primary:hover {
  box-shadow: 0 0 36px rgba(0, 212, 255, 0.5);
  transform: translateY(-2px);
}

.btn-outline {
  border: 1px solid var(--border-hover);
  color: var(--accent-cyan);
  background: transparent;
}

.btn-outline:hover {
  background: var(--accent-glow);
  transform: translateY(-2px);
}

/* Scroll hint */
.hero-scroll-hint {
  position: absolute;
  bottom: 36px;
  left: 50%;
  transform: translateX(-50%);
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 8px;
  color: var(--text-muted);
  font-size: 0.7rem;
  letter-spacing: 0.15em;
}

.scroll-line {
  width: 1px;
  height: 40px;
  background: linear-gradient(to bottom, var(--accent-cyan), transparent);
  animation: scrollDrop 1.8s ease-in-out infinite;
}

@keyframes scrollDrop {
  0%   { opacity: 0; transform: scaleY(0); transform-origin: top; }
  50%  { opacity: 1; transform: scaleY(1); }
  100% { opacity: 0; transform: scaleY(1); transform-origin: bottom; }
}

/* ============================================================
   CHAPTERS SECTION
   ============================================================ */
.chapters {
  max-width: 1200px;
  margin: 0 auto;
  padding: 100px 24px;
}

.section-header {
  text-align: center;
  margin-bottom: 64px;
}

.section-tag {
  font-size: 0.8rem;
  letter-spacing: 0.18em;
  color: var(--accent-cyan);
  margin-bottom: 12px;
  font-family: 'Courier New', monospace;
}

.section-title {
  font-size: clamp(1.8rem, 4vw, 2.8rem);
  font-weight: 700;
  margin-bottom: 16px;
  letter-spacing: -0.02em;
}

.section-desc {
  color: var(--text-secondary);
  font-size: 1rem;
}

/* Cards grid */
.cards-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
  gap: 24px;
}

/* Card */
.card {
  display: flex;
  flex-direction: column;
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 32px 28px;
  position: relative;
  overflow: hidden;
  transition: all var(--transition);
  cursor: pointer;
}

.card::before {
  content: '';
  position: absolute;
  inset: 0;
  background: linear-gradient(135deg, rgba(0,212,255,0.05), transparent 60%);
  opacity: 0;
  transition: opacity var(--transition);
}

.card:hover {
  border-color: var(--border-hover);
  background: var(--bg-card-hover);
  transform: translateY(-4px);
  box-shadow: 0 12px 40px rgba(0, 117, 255, 0.2);
}

.card:hover::before { opacity: 1; }

.card-icon {
  width: 44px;
  height: 44px;
  color: var(--accent-cyan);
  margin-bottom: 16px;
}

.card-icon svg {
  width: 100%;
  height: 100%;
}

.card-num {
  font-size: 0.72rem;
  letter-spacing: 0.15em;
  color: var(--text-muted);
  font-family: 'Courier New', monospace;
  margin-bottom: 8px;
}

.card-title {
  font-size: 1.35rem;
  font-weight: 700;
  margin-bottom: 12px;
  color: var(--text-primary);
}

.card-desc {
  font-size: 0.9rem;
  color: var(--text-secondary);
  line-height: 1.7;
  flex: 1;
}

.card-arrow {
  margin-top: 24px;
  font-size: 1.2rem;
  color: var(--accent-cyan);
  transition: transform var(--transition);
}

.card:hover .card-arrow {
  transform: translateX(6px);
}

/* ============================================================
   FOOTER
   ============================================================ */
.footer {
  background: var(--bg-surface);
  border-top: 1px solid var(--border);
  padding: 56px 24px 24px;
}

.footer-inner {
  max-width: 1200px;
  margin: 0 auto;
  display: grid;
  grid-template-columns: 1fr 1fr 1fr;
  gap: 40px;
  padding-bottom: 40px;
  border-bottom: 1px solid var(--border);
}

.footer-brand {
  font-size: 1rem;
  font-weight: 700;
}

.footer-brand p {
  margin-top: 8px;
  font-size: 0.82rem;
  color: var(--text-secondary);
  font-weight: 400;
}

.footer-links {
  display: flex;
  flex-direction: column;
  gap: 10px;
}

.footer-links a {
  font-size: 0.88rem;
  color: var(--text-secondary);
  transition: color var(--transition);
}

.footer-links a:hover { color: var(--accent-cyan); }

.footer-info p {
  font-size: 0.82rem;
  color: var(--text-secondary);
  margin-bottom: 6px;
  font-family: 'Courier New', monospace;
}

.footer-info .accent { color: var(--accent-cyan); }

.footer-bottom {
  max-width: 1200px;
  margin: 24px auto 0;
  font-size: 0.78rem;
  color: var(--text-muted);
  text-align: center;
}

/* ============================================================
   REVEAL ANIMATION
   ============================================================ */
.reveal {
  opacity: 0;
  transform: translateY(28px);
  transition: opacity 0.6s ease, transform 0.6s ease;
}

.reveal.visible {
  opacity: 1;
  transform: translateY(0);
}

/* Stagger for cards */
.card.reveal:nth-child(1) { transition-delay: 0.05s; }
.card.reveal:nth-child(2) { transition-delay: 0.12s; }
.card.reveal:nth-child(3) { transition-delay: 0.19s; }
.card.reveal:nth-child(4) { transition-delay: 0.26s; }
.card.reveal:nth-child(5) { transition-delay: 0.33s; }

/* ============================================================
   RESPONSIVE
   ============================================================ */
@media (max-width: 768px) {
  /* Nav */
  .nav-toggle {
    display: flex;
  }

  .nav-menu {
    display: none;
    position: absolute;
    top: var(--nav-height);
    left: 0; right: 0;
    background: rgba(8, 12, 20, 0.98);
    border-bottom: 1px solid var(--border);
    flex-direction: column;
    padding: 16px 24px;
    gap: 4px;
  }

  .nav-menu.open {
    display: flex;
  }

  .nav-link {
    padding: 12px 16px;
    font-size: 1rem;
  }

  /* Hero */
  .hero-desc br { display: none; }

  /* Cards */
  .cards-grid {
    grid-template-columns: 1fr;
  }

  /* Footer */
  .footer-inner {
    grid-template-columns: 1fr;
    gap: 28px;
  }
}

@media (max-width: 480px) {
  .hero-title { font-size: 2rem; }
  .btn { padding: 11px 24px; font-size: 0.9rem; }
}