/* ================================================
   GIẢI MÃ TÂM LÝ — Design System
   Palette: Deep Space + Neon Purple/Cyan
   ================================================ */

@import url('https://fonts.googleapis.com/css2?family=Inter:wght@300;400;500;600;700;800&display=swap');

:root {
  --bg-primary: #0a0a1a;
  --bg-secondary: #12122a;
  --bg-card: rgba(20, 20, 50, 0.6);
  --bg-card-hover: rgba(30, 30, 70, 0.7);
  --accent: #9b59f0;
  --accent-cyan: #00e5ff;
  --gradient: linear-gradient(135deg, #9b59f0, #00e5ff);
  --gradient-subtle: linear-gradient(135deg, rgba(155,89,240,0.15), rgba(0,229,255,0.1));
  --text-primary: #f0f0f5;
  --text-secondary: #a0a0c0;
  --text-muted: #6a6a8a;
  --border: rgba(155, 89, 240, 0.15);
  --border-hover: rgba(155, 89, 240, 0.4);
  --glow-purple: 0 0 30px rgba(155, 89, 240, 0.3);
  --glow-cyan: 0 0 30px rgba(0, 229, 255, 0.2);
  --radius: 16px;
  --radius-sm: 10px;
  --header-h: 72px;
  --transition: 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

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

html {
  scroll-behavior: smooth;
  overflow-x: hidden;
}

body {
  font-family: 'Inter', system-ui, -apple-system, sans-serif;
  background: var(--bg-primary);
  color: var(--text-primary);
  line-height: 1.7;
  overflow-x: hidden;
}

h1, h2, h3, h4, h5, h6 {
  scroll-margin-top: calc(var(--header-h) + 20px);
  line-height: 1.3;
}

a { color: var(--accent-cyan); text-decoration: none; transition: color var(--transition); }
a:hover { color: #66f0ff; }

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

.container {
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 24px;
}

/* ================= HEADER ================= */
.top-bar {
  position: fixed;
  top: 0; left: 0; width: 100%;
  height: var(--header-h);
  background: rgba(10, 10, 26, 0.85);
  backdrop-filter: blur(20px);
  -webkit-backdrop-filter: blur(20px);
  z-index: 1000;
  border-bottom: 1px solid var(--border);
  transition: background var(--transition);
}

.nav {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: var(--header-h);
}

.brand {
  display: flex;
  align-items: center;
  gap: 12px;
  text-decoration: none;
}

.brand-logo {
  width: 44px; height: 44px;
  object-fit: contain;
  border-radius: 12px;
  transition: transform var(--transition), box-shadow var(--transition);
}

.brand:hover .brand-logo {
  transform: scale(1.05);
  box-shadow: var(--glow-purple);
}

.brand-text {
  display: flex;
  flex-direction: column;
  line-height: 1.2;
}

.brand-title {
  font-size: 1.05rem;
  font-weight: 700;
  color: var(--text-primary);
  transition: color var(--transition);
}

.brand-sub {
  font-size: 0.78rem;
  color: var(--text-secondary);
  font-weight: 400;
}

.brand:hover .brand-title { color: var(--accent); }

.nav-links { display: flex; align-items: center; gap: 8px; }

.nav-links a {
  font-size: 14px;
  font-weight: 500;
  color: var(--text-secondary);
  text-decoration: none;
  padding: 6px 14px;
  border-radius: 8px;
  transition: all var(--transition);
}

.nav-links a:hover {
  color: var(--text-primary);
  background: var(--gradient-subtle);
}

.nav-links a.active {
  color: var(--accent-cyan);
  background: rgba(0, 229, 255, 0.08);
}

/* Mobile menu toggle */
.menu-toggle {
  display: none;
  background: none;
  border: none;
  color: var(--text-primary);
  font-size: 24px;
  cursor: pointer;
  padding: 8px;
}

/* ================= MAIN ================= */
main { padding-top: var(--header-h); }

/* ================= HERO ================= */
.hero {
  position: relative;
  padding: 100px 0 80px;
  overflow: hidden;
  min-height: 90vh;
  display: flex;
  align-items: center;
}

/* Neural network background */
.hero-bg {
  position: absolute;
  top: 0; left: 0; right: 0; bottom: 0;
  z-index: 0;
  overflow: hidden;
}

.hero-bg canvas { width: 100%; height: 100%; }

/* Gradient overlay */
.hero::after {
  content: '';
  position: absolute;
  bottom: 0; left: 0; right: 0;
  height: 200px;
  background: linear-gradient(to top, var(--bg-primary), transparent);
  z-index: 1;
  pointer-events: none;
}

.hero .container {
  position: relative;
  z-index: 2;
}

.hero-grid {
  display: grid;
  grid-template-columns: 1.1fr 0.9fr;
  gap: 60px;
  align-items: center;
}

.hero-text { max-width: 560px; }

.tagline {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  font-size: 13px;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 2px;
  color: var(--accent-cyan);
  margin-bottom: 20px;
  padding: 6px 16px;
  background: rgba(0, 229, 255, 0.08);
  border: 1px solid rgba(0, 229, 255, 0.2);
  border-radius: 30px;
}

.hero-text h1 {
  font-size: clamp(2.2rem, 4vw, 3.2rem);
  font-weight: 800;
  margin-bottom: 20px;
  background: var(--gradient);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.hero-desc {
  font-size: 1.05rem;
  color: var(--text-secondary);
  margin-bottom: 32px;
  line-height: 1.8;
}

.hero-actions {
  display: flex;
  gap: 16px;
  flex-wrap: wrap;
}

/* Buttons */
.btn {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 14px 28px;
  font-size: 15px;
  font-weight: 600;
  border-radius: var(--radius-sm);
  border: none;
  cursor: pointer;
  transition: all var(--transition);
  text-decoration: none;
  font-family: inherit;
}

.btn-primary {
  background: var(--gradient);
  color: #fff;
  box-shadow: 0 4px 20px rgba(155, 89, 240, 0.3);
}

.btn-primary:hover {
  transform: translateY(-2px);
  box-shadow: 0 8px 30px rgba(155, 89, 240, 0.5);
  color: #fff;
}

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

.btn-outline:hover {
  background: var(--gradient-subtle);
  border-color: var(--accent);
  transform: translateY(-2px);
  color: var(--text-primary);
}

/* Hero video card */
.hero-card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 20px;
  backdrop-filter: blur(10px);
  transition: all var(--transition);
  max-width: 480px;
}

.hero-card:hover {
  border-color: var(--border-hover);
  box-shadow: var(--glow-purple);
}

.hero-card h2 {
  font-size: 1rem;
  font-weight: 600;
  margin-bottom: 14px;
  color: var(--text-secondary);
}

/* YouTube Facade */
.lite-yt-facade {
  position: relative;
  display: block;
  background-color: #000;
  background-position: center;
  background-size: cover;
  cursor: pointer;
  border-radius: 12px;
  overflow: hidden;
  width: 100%;
  aspect-ratio: 16/9;
  box-shadow: 0 4px 20px rgba(0,0,0,0.4);
}

.lite-play-btn {
  width: 68px; height: 48px;
  position: absolute;
  background: rgba(155, 89, 240, 0.85);
  border-radius: 14px;
  border: none;
  top: 50%; left: 50%;
  transform: translate(-50%, -50%);
  transition: all var(--transition);
}

.lite-yt-facade:hover .lite-play-btn {
  background: var(--accent);
  box-shadow: var(--glow-purple);
  transform: translate(-50%, -50%) scale(1.1);
}

.lite-play-btn::before {
  content: '';
  border-style: solid;
  border-width: 11px 0 11px 21px;
  border-color: transparent transparent transparent #fff;
  position: absolute;
  top: 13px; left: 26px;
}

.link-yt {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  margin-top: 14px;
  font-size: 14px;
  font-weight: 500;
  color: var(--accent-cyan);
}

.link-yt:hover { color: #66f0ff; }

/* ================= SECTION BASE ================= */
.section { padding: 100px 0; }

.section-alt { background: var(--bg-secondary); }

.section-header {
  text-align: center;
  max-width: 650px;
  margin: 0 auto 60px;
}

.section-header h2 {
  font-size: clamp(1.8rem, 3vw, 2.4rem);
  font-weight: 700;
  margin-bottom: 16px;
}

.section-header h2 .gradient-text {
  background: var(--gradient);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.section-header p {
  font-size: 1rem;
  color: var(--text-secondary);
  line-height: 1.7;
}

/* ================= SHORTS / VIDEOS ================= */
.shorts-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
  gap: 20px;
}

.short-card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  overflow: hidden;
  transition: all var(--transition);
  cursor: pointer;
}

.short-card:hover {
  transform: translateY(-4px);
  border-color: var(--border-hover);
  box-shadow: var(--glow-purple);
}

.short-thumb {
  position: relative;
  aspect-ratio: 9/16;
  background-size: cover;
  background-position: center;
  overflow: hidden;
}

.short-thumb::after {
  content: '▶';
  position: absolute;
  top: 50%; left: 50%;
  transform: translate(-50%, -50%);
  font-size: 32px;
  color: #fff;
  text-shadow: 0 2px 10px rgba(0,0,0,0.5);
  opacity: 0;
  transition: opacity var(--transition);
}

.short-card:hover .short-thumb::after { opacity: 1; }

.short-info { padding: 14px; }

.short-info h3 {
  font-size: 13px;
  font-weight: 600;
  color: var(--text-primary);
  display: -webkit-box;
  -webkit-line-clamp: 2;
  -webkit-box-orient: vertical;
  overflow: hidden;
}

/* ================= TOPICS / CHỦ ĐỀ ================= */
.topics-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
  gap: 24px;
}

.topic-card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 32px 28px;
  backdrop-filter: blur(10px);
  transition: all var(--transition);
  text-decoration: none;
  display: block;
}

.topic-card:hover {
  transform: translateY(-6px);
  border-color: var(--accent);
  box-shadow: var(--glow-purple);
  background: var(--bg-card-hover);
}

.topic-icon {
  width: 56px; height: 56px;
  border-radius: 14px;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 28px;
  margin-bottom: 20px;
  background: var(--gradient-subtle);
  border: 1px solid var(--border);
}

.topic-card h3 {
  font-size: 1.15rem;
  font-weight: 700;
  margin-bottom: 10px;
  color: var(--text-primary);
}

.topic-card p {
  font-size: 0.9rem;
  color: var(--text-secondary);
  line-height: 1.6;
  margin-bottom: 16px;
}

.topic-link {
  font-size: 13px;
  font-weight: 600;
  color: var(--accent-cyan);
  display: inline-flex;
  align-items: center;
  gap: 4px;
}

.topic-card:hover .topic-link { gap: 8px; }

/* ================= BLOG PREVIEW ================= */
.blog-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(320px, 1fr));
  gap: 24px;
}

.blog-card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 28px;
  transition: all var(--transition);
  display: flex;
  flex-direction: column;
}

.blog-card:hover {
  transform: translateY(-4px);
  border-color: var(--border-hover);
  box-shadow: var(--glow-cyan);
}

.blog-tag {
  display: inline-block;
  padding: 4px 12px;
  font-size: 11px;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 1px;
  border-radius: 6px;
  margin-bottom: 16px;
  background: var(--gradient-subtle);
  color: var(--accent);
  border: 1px solid var(--border);
}

.blog-card h3 {
  font-size: 1.1rem;
  font-weight: 700;
  margin-bottom: 12px;
  color: var(--text-primary);
}

.blog-card p {
  font-size: 0.9rem;
  color: var(--text-secondary);
  line-height: 1.6;
  flex: 1;
}

.blog-card .read-more {
  margin-top: 16px;
  font-size: 13px;
  font-weight: 600;
  color: var(--accent-cyan);
  display: inline-flex;
  align-items: center;
  gap: 4px;
}

.blog-card:hover .read-more { gap: 8px; }

/* ================= ABOUT CHANNEL ================= */
.about-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 60px;
  align-items: center;
}

.about-content h2 {
  font-size: clamp(1.8rem, 3vw, 2.2rem);
  font-weight: 700;
  margin-bottom: 20px;
}

.about-content p {
  font-size: 1rem;
  color: var(--text-secondary);
  line-height: 1.8;
  margin-bottom: 16px;
}

.stats-row {
  display: flex;
  gap: 32px;
  margin: 32px 0;
}

.stat-item { text-align: center; }

.stat-number {
  font-size: 2rem;
  font-weight: 800;
  background: var(--gradient);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.stat-label {
  font-size: 0.85rem;
  color: var(--text-muted);
  margin-top: 4px;
}

.about-visual {
  display: flex;
  justify-content: center;
  align-items: center;
}

.about-avatar {
  width: 260px; height: 260px;
  border-radius: 50%;
  object-fit: cover;
  border: 3px solid var(--accent);
  box-shadow: var(--glow-purple), 0 0 60px rgba(155,89,240,0.15);
  transition: all var(--transition);
}

.about-avatar:hover {
  transform: scale(1.03);
  box-shadow: var(--glow-purple), 0 0 80px rgba(155,89,240,0.25);
}

/* ================= CONTACT ================= */
.contact-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 48px;
}

.contact-info h3,
.contact-connect h3 {
  font-size: 1.3rem;
  font-weight: 700;
  margin-bottom: 20px;
}

.contact-item {
  display: flex;
  align-items: center;
  gap: 12px;
  padding: 14px 0;
  border-bottom: 1px solid var(--border);
}

.contact-item:last-child { border-bottom: none; }

.contact-icon {
  width: 40px; height: 40px;
  border-radius: 10px;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 18px;
  background: var(--gradient-subtle);
  border: 1px solid var(--border);
  flex-shrink: 0;
}

.contact-item span {
  font-size: 0.95rem;
  color: var(--text-secondary);
}

.contact-item a {
  color: var(--accent-cyan);
  font-weight: 500;
}

.social-links {
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: 12px;
}

.social-link {
  display: flex;
  align-items: center;
  gap: 12px;
  padding: 14px 18px;
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  transition: all var(--transition);
  text-decoration: none;
  color: var(--text-primary);
  font-weight: 500;
}

.social-link:hover {
  border-color: var(--accent);
  background: var(--bg-card-hover);
  transform: translateX(4px);
  color: var(--text-primary);
}

.social-link .icon {
  font-size: 22px;
  width: 32px;
  text-align: center;
}

/* ================= FOOTER ================= */
.footer {
  padding: 40px 0;
  text-align: center;
  border-top: 1px solid var(--border);
  color: var(--text-muted);
  font-size: 0.85rem;
}

/* ================= ANIMATIONS ================= */
.fade-in {
  opacity: 0;
  transform: translateY(30px);
  transition: opacity 0.6s ease, transform 0.6s ease;
}

.fade-in.visible {
  opacity: 1;
  transform: translateY(0);
}

/* Stagger animation delay */
.fade-in:nth-child(1) { transition-delay: 0s; }
.fade-in:nth-child(2) { transition-delay: 0.1s; }
.fade-in:nth-child(3) { transition-delay: 0.2s; }
.fade-in:nth-child(4) { transition-delay: 0.3s; }

/* Pulse glow for CTA */
@keyframes pulse-glow {
  0%, 100% { box-shadow: 0 4px 20px rgba(155,89,240,0.3); }
  50% { box-shadow: 0 4px 40px rgba(155,89,240,0.6); }
}

.btn-primary { animation: pulse-glow 3s ease-in-out infinite; }
.btn-primary:hover { animation: none; }

/* ================= RESPONSIVE ================= */
@media (max-width: 900px) {
  .hero-grid,
  .about-grid { grid-template-columns: 1fr; }

  .hero-card { max-width: 100%; }

  .hero { min-height: auto; padding: 80px 0 60px; }

  .about-visual { order: -1; }
  .about-avatar { width: 180px; height: 180px; }

  .contact-grid { grid-template-columns: 1fr; }
  .stats-row { justify-content: center; }
}

@media (max-width: 768px) {
  :root { --header-h: auto; }

  .top-bar {
    height: auto;
    padding: 12px 0;
  }

  .nav {
    flex-wrap: wrap;
    height: auto;
    gap: 10px;
  }

  .nav-links {
    display: none;
    flex-direction: column;
    width: 100%;
    gap: 4px;
    padding-top: 8px;
    border-top: 1px solid var(--border);
  }

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

  .nav-links a {
    width: 100%;
    padding: 10px 14px;
    font-size: 15px;
  }

  .menu-toggle { display: block; }

  main { padding-top: 72px; }

  .hero-text h1 { font-size: 1.8rem; }
  .hero-actions { flex-direction: column; }
  .btn { width: 100%; justify-content: center; }

  .section { padding: 60px 0; }
  .section-header { margin-bottom: 40px; }

  .shorts-grid { grid-template-columns: repeat(2, 1fr); }
  .blog-grid { grid-template-columns: 1fr; }
  .topics-grid { grid-template-columns: 1fr; }
}

@media (max-width: 480px) {
  .brand-sub { display: none; }
  .shorts-grid { grid-template-columns: repeat(2, 1fr); gap: 12px; }
  .stats-row { gap: 20px; }
  .stat-number { font-size: 1.5rem; }
}