/* ==========================================================================
   AI STEM ROBOTICS - DESIGN SYSTEM & STYLESHEET
   Giảng viên: Nguyễn Hùng AI STEM
   Author: Antigravity
   ========================================================================== */

:root {
  /* Color Palette */
  --bg-dark: #07090e;
  --bg-card: rgba(15, 23, 42, 0.75);
  --bg-card-hover: rgba(30, 41, 59, 0.85);
  --bg-elevated: #0f172a;
  
  --primary: #00e5ff;
  --primary-glow: rgba(0, 229, 255, 0.35);
  --primary-dark: #0099cc;
  
  --secondary: #6366f1;
  --secondary-glow: rgba(99, 102, 241, 0.35);
  
  --accent-pink: #ec4899;
  --accent-emerald: #10b981;
  --accent-amber: #f59e0b;
  
  --text-main: #f8fafc;
  --text-muted: #94a3b8;
  --text-dim: #64748b;
  
  --border-glass: rgba(255, 255, 255, 0.1);
  --border-focus: rgba(0, 229, 255, 0.5);
  
  /* Gradients */
  --grad-primary: linear-gradient(135deg, #00e5ff 0%, #6366f1 100%);
  --grad-hot: linear-gradient(135deg, #f43f5e 0%, #fb923c 100%);
  --grad-emerald: linear-gradient(135deg, #10b981 0%, #06b6d4 100%);
  --grad-dark-card: linear-gradient(180deg, rgba(30, 41, 59, 0.7) 0%, rgba(15, 23, 42, 0.8) 100%);
  --grad-glow-sphere: radial-gradient(circle, rgba(0, 229, 255, 0.15) 0%, rgba(99, 102, 241, 0.05) 50%, transparent 70%);

  /* Typography */
  --font-heading: 'Plus Jakarta Sans', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
  --font-body: 'Plus Jakarta Sans', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;

  /* Spacing & Layout */
  --max-width: 1240px;
  --radius-sm: 8px;
  --radius-md: 14px;
  --radius-lg: 20px;
  --radius-full: 9999px;
  
  /* Transitions */
  --transition-fast: 0.2s cubic-bezier(0.4, 0, 0.2, 1);
  --transition-normal: 0.35s cubic-bezier(0.4, 0, 0.2, 1);
}

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

html {
  scroll-behavior: smooth;
  font-size: 16px;
  color-scheme: dark;
  overflow-x: hidden;
  width: 100%;
  max-width: 100vw;
}

body {
  font-family: var(--font-body);
  background-color: var(--bg-dark);
  color: var(--text-main);
  line-height: 1.6;
  overflow-x: hidden;
  width: 100%;
  max-width: 100vw;
  position: relative;
  background-image: 
    radial-gradient(circle at 15% 15%, rgba(0, 229, 255, 0.07) 0%, transparent 40%),
    radial-gradient(circle at 85% 30%, rgba(99, 102, 241, 0.08) 0%, transparent 50%),
    radial-gradient(circle at 50% 80%, rgba(236, 72, 153, 0.05) 0%, transparent 50%);
  background-attachment: fixed;
}

/* Background Grid Overlay */
.bg-grid-overlay {
  position: fixed;
  inset: 0;
  background-size: 40px 40px;
  background-image: 
    linear-gradient(to right, rgba(255, 255, 255, 0.02) 1px, transparent 1px),
    linear-gradient(to bottom, rgba(255, 255, 255, 0.02) 1px, transparent 1px);
  pointer-events: none;
  z-index: 0;
}

/* Layout Utilities */
.container {
  width: 100%;
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 1.5rem;
  position: relative;
  z-index: 1;
}

section {
  padding: 6rem 0;
  position: relative;
}

/* Typography Helpers */
h1, h2, h3, h4, h5, h6 {
  font-family: var(--font-heading);
  font-weight: 700;
  line-height: 1.25;
  color: #ffffff;
}

.text-gradient {
  background: var(--grad-primary);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  display: inline-block;
}

.text-gradient-hot {
  background: var(--grad-hot);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  display: inline-block;
}

.section-header {
  text-align: center;
  max-width: 760px;
  margin: 0 auto 4rem auto;
}

.section-tag {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  padding: 0.4rem 1rem;
  background: rgba(0, 229, 255, 0.08);
  border: 1px solid rgba(0, 229, 255, 0.25);
  border-radius: var(--radius-full);
  color: var(--primary);
  font-size: 0.85rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  margin-bottom: 1rem;
}

.section-title {
  font-size: clamp(2rem, 3.5vw, 2.75rem);
  letter-spacing: -0.02em;
  margin-bottom: 1.25rem;
}

.section-desc {
  font-size: 1.125rem;
  color: var(--text-muted);
}

/* Buttons */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 0.6rem;
  font-family: var(--font-heading);
  font-weight: 600;
  font-size: 1rem;
  padding: 0.85rem 1.75rem;
  border-radius: var(--radius-full);
  text-decoration: none;
  cursor: pointer;
  transition: all var(--transition-normal);
  border: none;
  outline: none;
  white-space: nowrap;
}

.btn-primary {
  background: var(--grad-primary);
  color: #07090e;
  box-shadow: 0 4px 20px var(--primary-glow);
}

.btn-primary:hover {
  transform: translateY(-2px);
  box-shadow: 0 8px 30px rgba(0, 229, 255, 0.5);
  color: #000;
}

.btn-secondary {
  background: rgba(255, 255, 255, 0.07);
  color: #fff;
  border: 1px solid var(--border-glass);
  backdrop-filter: blur(10px);
}

.btn-secondary:hover {
  background: rgba(255, 255, 255, 0.12);
  border-color: rgba(255, 255, 255, 0.25);
  transform: translateY(-2px);
  color: var(--primary);
}

.btn-sm {
  padding: 0.55rem 1.25rem;
  font-size: 0.875rem;
}

.btn-lg {
  padding: 1.1rem 2.25rem;
  font-size: 1.1rem;
}

/* Glassmorphism Card */
.glass-card {
  background: var(--grad-dark-card);
  backdrop-filter: blur(16px);
  -webkit-backdrop-filter: blur(16px);
  border: 1px solid var(--border-glass);
  border-radius: var(--radius-lg);
  box-shadow: 0 20px 40px rgba(0, 0, 0, 0.4);
  transition: all var(--transition-normal);
  overflow: hidden;
  position: relative;
}

.glass-card:hover {
  border-color: rgba(0, 229, 255, 0.3);
  box-shadow: 0 25px 50px rgba(0, 0, 0, 0.6), 0 0 30px rgba(0, 229, 255, 0.1);
}

/* ==========================================================================
   HEADER & NAVBAR
   ========================================================================== */
.navbar {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 80px;
  z-index: 1000;
  transition: all var(--transition-normal);
  border-bottom: 1px solid transparent;
}

.navbar.scrolled {
  background: rgba(7, 9, 14, 0.85);
  backdrop-filter: blur(20px);
  -webkit-backdrop-filter: blur(20px);
  border-bottom-color: var(--border-glass);
  height: 70px;
}

.nav-container {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 100%;
}

.brand-logo {
  display: flex;
  align-items: center;
  gap: 0.85rem;
  text-decoration: none;
  transition: transform 0.25s ease;
  flex-shrink: 0;
}

.brand-logo:hover {
  transform: translateY(-1px);
}

.logo-icon-box {
  width: 48px;
  height: 48px;
  border-radius: 14px;
  background: linear-gradient(135deg, rgba(14, 165, 233, 0.15), rgba(99, 102, 241, 0.25));
  border: 1.5px solid rgba(56, 189, 248, 0.45);
  display: flex;
  align-items: center;
  justify-content: center;
  box-shadow: 0 0 20px rgba(14, 165, 233, 0.25), inset 0 0 12px rgba(56, 189, 248, 0.12);
  position: relative;
  transition: all 0.3s cubic-bezier(0.16, 1, 0.3, 1);
}

.logo-icon-box::before {
  content: '';
  position: absolute;
  inset: 0;
  border-radius: 13px;
  background: radial-gradient(circle at 50% 30%, rgba(56, 189, 248, 0.25), transparent 70%);
  pointer-events: none;
}

.brand-logo:hover .logo-icon-box {
  border-color: #38bdf8;
  box-shadow: 0 0 26px rgba(56, 189, 248, 0.55), inset 0 0 15px rgba(56, 189, 248, 0.25);
}

.robot-logo-svg {
  position: relative;
  z-index: 1;
  transition: transform 0.3s ease;
}

.brand-logo:hover .robot-logo-svg {
  transform: scale(1.06);
}

.robot-visor {
  transition: filter 0.3s ease;
  filter: drop-shadow(0 0 3px #00f2fe);
}

.brand-logo:hover .robot-visor {
  filter: drop-shadow(0 0 7px #00f2fe) drop-shadow(0 0 12px #38bdf8);
}

.robot-light {
  filter: drop-shadow(0 0 3px #00f2fe);
  animation: pulse-robot-light 2.5s infinite alternate ease-in-out;
}

@keyframes pulse-robot-light {
  0% { opacity: 0.65; filter: drop-shadow(0 0 2px #00f2fe); }
  100% { opacity: 1; filter: drop-shadow(0 0 6px #00f2fe) drop-shadow(0 0 10px #38bdf8); }
}

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

.brand-title {
  font-size: 1.15rem;
  font-weight: 800;
  color: #ffffff;
  letter-spacing: -0.01em;
  display: flex;
  align-items: center;
  gap: 0.35rem;
}

.brand-title .text-gradient {
  background: linear-gradient(135deg, #38bdf8 0%, #818cf8 100%);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
}

.brand-subtitle {
  font-size: 0.68rem;
  color: #38bdf8;
  font-weight: 700;
  letter-spacing: 0.08em;
  text-transform: uppercase;
}

.nav-links {
  display: flex;
  align-items: center;
  list-style: none;
  gap: clamp(0.75rem, 1.25vw, 1.35rem);
  margin-left: auto;
}

.nav-link {
  color: var(--text-muted);
  text-decoration: none;
  font-weight: 500;
  font-size: 0.9rem;
  transition: color var(--transition-fast);
  position: relative;
  white-space: nowrap;
}

.nav-link:hover, .nav-link.active {
  color: var(--primary);
}

.nav-link::after {
  content: '';
  position: absolute;
  bottom: -4px;
  left: 0;
  width: 0;
  height: 2px;
  background: var(--primary);
  transition: width var(--transition-fast);
  border-radius: 2px;
}

.nav-link:hover::after {
  width: 100%;
}

.nav-cta-group {
  display: flex;
  align-items: center;
  gap: 1rem;
}

.mobile-toggle {
  display: none;
  background: none;
  border: none;
  color: #fff;
  cursor: pointer;
  padding: 0.5rem;
}

.mobile-menu-drawer {
  display: none;
}

/* ==========================================================================
   HERO SECTION
   ========================================================================== */
.hero-section {
  padding-top: 140px;
  padding-bottom: 6rem;
  min-height: 90vh;
  display: flex;
  align-items: center;
  position: relative;
}

.hero-grid {
  display: grid;
  grid-template-columns: 1.15fr 0.85fr;
  gap: 3.5rem;
  align-items: center;
}

.hero-badge-wrap {
  display: inline-flex;
  align-items: center;
  gap: 0.6rem;
  padding: 0.45rem 1.1rem;
  border-radius: var(--radius-full);
  background: rgba(99, 102, 241, 0.12);
  border: 1px solid rgba(99, 102, 241, 0.3);
  margin-bottom: 1.5rem;
}

.hero-badge-dot {
  width: 8px;
  height: 8px;
  border-radius: 50%;
  background: #10b981;
  box-shadow: 0 0 10px #10b981;
  animation: pulse-dot 2s infinite;
}

@keyframes pulse-dot {
  0%, 100% { opacity: 1; transform: scale(1); }
  50% { opacity: 0.4; transform: scale(0.85); }
}

.hero-badge-text {
  font-size: 0.85rem;
  font-weight: 600;
  color: #e0e7ff;
}

.hero-title {
  font-size: clamp(2.3rem, 4.5vw, 3.6rem);
  line-height: 1.15;
  letter-spacing: -0.03em;
  margin-bottom: 1.5rem;
}

.hero-desc {
  font-size: 1.15rem;
  color: var(--text-muted);
  line-height: 1.7;
  margin-bottom: 2.25rem;
  max-width: 600px;
}

.hero-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 1.25rem;
  margin-bottom: 3rem;
}

.hero-stats-row {
  display: flex;
  gap: 2.5rem;
  border-top: 1px solid var(--border-glass);
  padding-top: 2rem;
}

.stat-item {
  display: flex;
  flex-direction: column;
}

.stat-num {
  font-size: 1.85rem;
  font-weight: 800;
  color: #fff;
  font-family: var(--font-heading);
}

.stat-label {
  font-size: 0.85rem;
  color: var(--text-muted);
  font-weight: 500;
}

/* Hero Media Box */
.hero-media-wrapper {
  position: relative;
}

.hero-media-glow {
  position: absolute;
  inset: -15px;
  background: var(--grad-primary);
  opacity: 0.25;
  filter: blur(40px);
  border-radius: var(--radius-lg);
  z-index: 0;
  animation: float-glow 6s ease-in-out infinite alternate;
}

@keyframes float-glow {
  0% { transform: scale(0.96) translateY(5px); opacity: 0.2; }
  100% { transform: scale(1.04) translateY(-5px); opacity: 0.35; }
}

.hero-image-card {
  position: relative;
  z-index: 1;
  border-radius: var(--radius-lg);
  overflow: hidden;
  border: 1px solid rgba(255, 255, 255, 0.15);
  box-shadow: 0 25px 60px rgba(0, 0, 0, 0.7);
  background: var(--bg-elevated);
}

.hero-image-card img {
  width: 100%;
  height: auto;
  display: block;
  object-fit: cover;
  transition: transform 0.6s ease;
}

.hero-image-card:hover img {
  transform: scale(1.03);
}

.hero-float-badge {
  position: absolute;
  bottom: 1.5rem;
  left: 1.5rem;
  right: 1.5rem;
  background: rgba(15, 23, 42, 0.85);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border: 1px solid rgba(255, 255, 255, 0.15);
  border-radius: var(--radius-md);
  padding: 1rem 1.25rem;
  display: flex;
  align-items: center;
  gap: 1rem;
  box-shadow: 0 10px 25px rgba(0, 0, 0, 0.5);
}

.float-badge-icon {
  width: 42px;
  height: 42px;
  border-radius: 10px;
  background: rgba(0, 229, 255, 0.15);
  color: var(--primary);
  display: flex;
  align-items: center;
  justify-content: center;
  flex-shrink: 0;
}

.float-badge-title {
  font-size: 0.95rem;
  font-weight: 700;
  color: #fff;
}

.float-badge-desc {
  font-size: 0.8rem;
  color: var(--text-muted);
}

/* ==========================================================================
   COURSES SECTION (3 TIERS)
   ========================================================================== */
.courses-section {
  position: relative;
}

.course-cards-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 2rem;
  align-items: stretch;
}

.course-card {
  display: flex;
  flex-direction: column;
  position: relative;
  transition: all var(--transition-normal);
}

.course-card.highlighted {
  border-color: rgba(0, 229, 255, 0.45);
  box-shadow: 0 0 35px rgba(0, 229, 255, 0.18), 0 20px 40px rgba(0, 0, 0, 0.5);
  transform: translateY(-8px);
}

.card-top-ribbon {
  position: absolute;
  top: 1rem;
  right: 1rem;
  background: var(--grad-hot);
  color: #fff;
  font-size: 0.75rem;
  font-weight: 700;
  padding: 0.3rem 0.85rem;
  border-radius: var(--radius-full);
  letter-spacing: 0.05em;
  text-transform: uppercase;
  z-index: 2;
  box-shadow: 0 4px 15px rgba(244, 63, 94, 0.4);
}

.course-image-thumb {
  height: 210px;
  position: relative;
  overflow: hidden;
  border-bottom: 1px solid var(--border-glass);
}

.course-image-thumb img {
  width: 100%;
  height: 100%;
  object-fit: cover;
  transition: transform 0.5s ease;
}

.course-card:hover .course-image-thumb img {
  transform: scale(1.06);
}

.course-level-tag {
  position: absolute;
  bottom: 0.75rem;
  left: 0.75rem;
  background: rgba(15, 23, 42, 0.85);
  backdrop-filter: blur(8px);
  padding: 0.3rem 0.75rem;
  border-radius: var(--radius-sm);
  font-size: 0.75rem;
  font-weight: 600;
  color: var(--primary);
  border: 1px solid rgba(0, 229, 255, 0.2);
}

.course-body {
  padding: 1.75rem;
  display: flex;
  flex-direction: column;
  flex: 1;
}

.course-header {
  margin-bottom: 1.25rem;
}

.course-number {
  font-size: 0.8rem;
  font-weight: 700;
  color: var(--primary);
  text-transform: uppercase;
  letter-spacing: 0.08em;
  margin-bottom: 0.35rem;
}

.course-name {
  font-size: 1.35rem;
  font-weight: 700;
  line-height: 1.3;
  margin-bottom: 0.75rem;
}

.course-short-desc {
  font-size: 0.925rem;
  color: var(--text-muted);
  line-height: 1.6;
}

/* Pricing Block */
.pricing-box {
  background: rgba(255, 255, 255, 0.03);
  border: 1px solid rgba(255, 255, 255, 0.06);
  border-radius: var(--radius-md);
  padding: 1.25rem;
  margin-bottom: 1.5rem;
}

.price-main {
  display: flex;
  align-items: baseline;
  gap: 0.5rem;
  margin-bottom: 0.35rem;
}

.price-amount {
  font-size: 2rem;
  font-weight: 800;
  color: #fff;
  font-family: var(--font-heading);
}

.price-duration {
  font-size: 0.95rem;
  color: var(--primary);
  font-weight: 600;
}

.price-note {
  font-size: 0.8rem;
  color: var(--text-dim);
}

/* Feature List */
.course-features {
  list-style: none;
  margin-bottom: 2rem;
  display: flex;
  flex-direction: column;
  gap: 0.75rem;
  flex: 1;
}

.feature-item {
  display: flex;
  align-items: flex-start;
  gap: 0.75rem;
  font-size: 0.9rem;
  color: #cbd5e1;
  line-height: 1.5;
}

.feature-icon {
  width: 18px;
  height: 18px;
  color: var(--accent-emerald);
  flex-shrink: 0;
  margin-top: 2px;
}

.course-target {
  font-size: 0.825rem;
  color: var(--text-dim);
  background: rgba(255, 255, 255, 0.02);
  border-radius: var(--radius-sm);
  padding: 0.75rem;
  margin-bottom: 1.5rem;
  border-left: 3px solid var(--primary);
}

.course-target strong {
  color: #e2e8f0;
}

/* ==========================================================================
   STUDY MODES (3 HÌNH THỨC HỌC)
   ========================================================================== */
.study-modes-section {
  position: relative;
  background: radial-gradient(circle at 50% 50%, rgba(99, 102, 241, 0.08) 0%, transparent 60%);
}

.study-modes-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 2rem;
  align-items: stretch;
}

.mode-card {
  padding: 2.25rem 2rem;
  display: flex;
  flex-direction: column;
  justify-content: space-between;
  border-radius: var(--radius-lg);
  position: relative;
  transition: all var(--transition-normal);
}

.mode-card:hover {
  transform: translateY(-6px);
  border-color: rgba(0, 229, 255, 0.4);
}

.mode-card.special {
  border-color: rgba(245, 158, 11, 0.45);
  box-shadow: 0 0 30px rgba(245, 158, 11, 0.15);
}

.mode-card.special:hover {
  border-color: rgba(245, 158, 11, 0.7);
  box-shadow: 0 0 40px rgba(245, 158, 11, 0.25);
}

.mode-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: 1.5rem;
}

.mode-icon-box {
  width: 52px;
  height: 52px;
  border-radius: 14px;
  background: rgba(0, 229, 255, 0.12);
  color: var(--primary);
  display: flex;
  align-items: center;
  justify-content: center;
}

.mode-card.special .mode-icon-box {
  background: rgba(245, 158, 11, 0.15);
  color: var(--accent-amber);
}

.mode-badge {
  font-size: 0.75rem;
  font-weight: 700;
  padding: 0.35rem 0.8rem;
  border-radius: var(--radius-full);
  text-transform: uppercase;
  letter-spacing: 0.05em;
  background: rgba(255, 255, 255, 0.06);
  color: var(--text-muted);
  border: 1px solid var(--border-glass);
}

.mode-card.special .mode-badge {
  background: rgba(245, 158, 11, 0.12);
  color: var(--accent-amber);
  border-color: rgba(245, 158, 11, 0.3);
}

.mode-title {
  font-size: 1.35rem;
  font-weight: 700;
  margin-bottom: 0.75rem;
  color: #fff;
}

.mode-desc {
  font-size: 0.925rem;
  color: var(--text-muted);
  line-height: 1.6;
  margin-bottom: 1.5rem;
}

.mode-bullets {
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: 0.75rem;
  margin-bottom: 2rem;
  flex: 1;
}

.mode-bullet-item {
  display: flex;
  align-items: flex-start;
  gap: 0.65rem;
  font-size: 0.875rem;
  color: #cbd5e1;
}

.mode-bullet-icon {
  width: 16px;
  height: 16px;
  color: var(--accent-emerald);
  flex-shrink: 0;
  margin-top: 3px;
}

.mode-card.special .mode-bullet-icon {
  color: var(--accent-amber);
}

.mode-price-tag {
  background: rgba(255, 255, 255, 0.03);
  border: 1px solid var(--border-glass);
  border-radius: var(--radius-md);
  padding: 1rem;
  margin-bottom: 1.5rem;
  text-align: center;
}

.mode-price-label {
  font-size: 0.75rem;
  color: var(--text-dim);
  text-transform: uppercase;
  letter-spacing: 0.05em;
  margin-bottom: 0.25rem;
}

.mode-price-value {
  font-size: 1.15rem;
  font-weight: 700;
  color: #fff;
}

.mode-card.special .mode-price-value {
  color: var(--accent-amber);
}

/* ==========================================================================
   INTERACTIVE SYLLABUS TABS & ACCORDION
   ========================================================================== */
.syllabus-section {
  background: rgba(15, 23, 42, 0.4);
}

.syllabus-tab-controls {
  display: flex;
  justify-content: center;
  gap: 1rem;
  margin-bottom: 3rem;
  flex-wrap: wrap;
}

.tab-btn {
  background: rgba(255, 255, 255, 0.05);
  border: 1px solid var(--border-glass);
  color: var(--text-muted);
  padding: 0.85rem 1.75rem;
  border-radius: var(--radius-full);
  font-family: var(--font-heading);
  font-weight: 600;
  font-size: 0.95rem;
  cursor: pointer;
  transition: all var(--transition-fast);
}

.tab-btn:hover {
  color: #fff;
  border-color: rgba(255, 255, 255, 0.2);
}

.tab-btn.active {
  background: var(--grad-primary);
  color: #07090e;
  border-color: transparent;
  box-shadow: 0 4px 20px var(--primary-glow);
}

.tab-pane {
  display: none;
  animation: fadeIn 0.4s ease;
}

.tab-pane.active {
  display: block;
}

@keyframes fadeIn {
  from { opacity: 0; transform: translateY(10px); }
  to { opacity: 1; transform: translateY(0); }
}

.accordion-list {
  display: flex;
  flex-direction: column;
  gap: 1rem;
  max-width: 900px;
  margin: 0 auto;
}

.accordion-item {
  border: 1px solid var(--border-glass);
  border-radius: var(--radius-md);
  background: rgba(15, 23, 42, 0.65);
  overflow: hidden;
  transition: border-color var(--transition-fast);
}

.accordion-item:hover {
  border-color: rgba(0, 229, 255, 0.25);
}

.accordion-header {
  padding: 1.25rem 1.5rem;
  display: flex;
  align-items: center;
  justify-content: space-between;
  cursor: pointer;
  background: transparent;
  border: none;
  width: 100%;
  text-align: left;
  color: #fff;
}

.acc-title-group {
  display: flex;
  align-items: center;
  gap: 1.25rem;
}

.session-badge {
  background: rgba(0, 229, 255, 0.12);
  color: var(--primary);
  font-size: 0.8rem;
  font-weight: 700;
  padding: 0.35rem 0.8rem;
  border-radius: var(--radius-sm);
  white-space: nowrap;
}

.session-name {
  font-size: 1.05rem;
  font-weight: 600;
}

.acc-arrow {
  width: 20px;
  height: 20px;
  color: var(--text-muted);
  transition: transform var(--transition-fast);
}

.accordion-item.open .acc-arrow {
  transform: rotate(180deg);
  color: var(--primary);
}

.accordion-content {
  max-height: 0;
  overflow: hidden;
  transition: max-height 0.35s cubic-bezier(0.4, 0, 0.2, 1);
  background: rgba(0, 0, 0, 0.2);
}

.accordion-body {
  padding: 1.25rem 1.5rem;
  border-top: 1px solid rgba(255, 255, 255, 0.05);
  color: #cbd5e1;
  font-size: 0.95rem;
  line-height: 1.6;
}

.lesson-points {
  margin-top: 0.75rem;
  padding-left: 1.25rem;
  display: flex;
  flex-direction: column;
  gap: 0.4rem;
}

/* ==========================================================================
   COMPARISON MATRIX TABLE
   ========================================================================== */
.mobile-table-hint {
  display: none;
  align-items: center;
  justify-content: center;
  gap: 0.5rem;
  font-size: 0.82rem;
  color: var(--primary);
  background: rgba(0, 229, 255, 0.08);
  border: 1px dashed rgba(0, 229, 255, 0.35);
  border-radius: var(--radius-full);
  padding: 0.45rem 1rem;
  margin-bottom: 1.25rem;
  text-align: center;
}

.table-wrapper {
  overflow-x: auto;
  -webkit-overflow-scrolling: touch;
  border-radius: var(--radius-lg);
  border: 1px solid var(--border-glass);
  background: var(--grad-dark-card);
  backdrop-filter: blur(16px);
}

.matrix-table {
  width: 100%;
  min-width: 640px;
  border-collapse: collapse;
  text-align: left;
}

.matrix-table th, .matrix-table td {
  padding: 1.25rem 1.5rem;
  border-bottom: 1px solid rgba(255, 255, 255, 0.06);
}

.matrix-table th {
  background: rgba(15, 23, 42, 0.9);
  font-weight: 700;
  font-size: 1.05rem;
  color: #fff;
}

.matrix-table th:first-child {
  width: 32%;
}

.matrix-table th.col-highlight {
  background: rgba(0, 229, 255, 0.08);
  color: var(--primary);
  border-top: 2px solid var(--primary);
}

.matrix-table td.col-highlight {
  background: rgba(0, 229, 255, 0.02);
}

.matrix-table tr:last-child td {
  border-bottom: none;
}

.table-check {
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
  color: var(--accent-emerald);
  font-weight: 600;
}

.table-cross {
  color: var(--text-dim);
}

/* ==========================================================================
   TUITION CALCULATOR
   ========================================================================== */
.calculator-box {
  max-width: 840px;
  margin: 0 auto;
  padding: 2.5rem;
}

.calc-options-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 2rem;
  margin-bottom: 2rem;
}

.calc-group label {
  display: block;
  font-weight: 600;
  margin-bottom: 0.75rem;
  color: #fff;
  font-size: 0.95rem;
}

.select-custom {
  width: 100%;
  padding: 0.9rem 1.25rem;
  background: rgba(15, 23, 42, 0.85);
  border: 1px solid var(--border-glass);
  border-radius: var(--radius-md);
  color: #fff;
  font-family: var(--font-body);
  font-size: 0.95rem;
  outline: none;
  cursor: pointer;
  transition: border-color var(--transition-fast);
}

.select-custom:focus {
  border-color: var(--primary);
}

.calc-radio-group {
  display: flex;
  flex-direction: column;
  gap: 0.75rem;
}

.radio-card {
  display: flex;
  align-items: center;
  gap: 1rem;
  padding: 0.85rem 1.2rem;
  background: rgba(255, 255, 255, 0.03);
  border: 1px solid var(--border-glass);
  border-radius: var(--radius-md);
  cursor: pointer;
  transition: all var(--transition-fast);
}

.radio-card:hover {
  background: rgba(255, 255, 255, 0.06);
  border-color: rgba(255, 255, 255, 0.2);
}

.radio-card.active {
  border-color: var(--primary);
  background: rgba(0, 229, 255, 0.08);
}

.radio-card input[type="radio"] {
  accent-color: var(--primary);
  width: 18px;
  height: 18px;
}

.calc-result-panel {
  border-top: 1px solid var(--border-glass);
  padding-top: 2rem;
  display: flex;
  align-items: center;
  justify-content: space-between;
  flex-wrap: wrap;
  gap: 1.5rem;
}

.calc-total-label {
  font-size: 0.9rem;
  color: var(--text-muted);
}

.calc-total-val {
  font-size: 2.2rem;
  font-weight: 800;
  color: var(--primary);
  font-family: var(--font-heading);
}

/* ==========================================================================
   INSTRUCTOR BIO SECTION
   ========================================================================== */
.instructor-grid {
  display: grid;
  grid-template-columns: 0.9fr 1.1fr;
  gap: 4rem;
  align-items: center;
}

.instructor-image-frame {
  position: relative;
  border-radius: var(--radius-lg);
  overflow: hidden;
  border: 1px solid rgba(255, 255, 255, 0.15);
  box-shadow: 0 25px 50px rgba(0, 0, 0, 0.6);
}

.instructor-image-frame img {
  width: 100%;
  height: auto;
  display: block;
  object-fit: cover;
}

.instructor-badge-overlay {
  position: absolute;
  bottom: 1.5rem;
  left: 1.5rem;
  right: 1.5rem;
  background: rgba(15, 23, 42, 0.9);
  backdrop-filter: blur(12px);
  padding: 1rem 1.25rem;
  border-radius: var(--radius-md);
  border: 1px solid rgba(255, 255, 255, 0.1);
}

.ins-name {
  font-size: 1.35rem;
  font-weight: 800;
  color: #fff;
}

.ins-role {
  font-size: 0.85rem;
  color: var(--primary);
  font-weight: 600;
}

.instructor-bio-content {
  display: flex;
  flex-direction: column;
  gap: 1.5rem;
}

.bio-paragraph {
  color: #cbd5e1;
  font-size: 1.05rem;
  line-height: 1.7;
}

.credential-badges {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 1.25rem;
  margin: 0.5rem 0;
}

.cred-item {
  display: flex;
  align-items: flex-start;
  gap: 0.85rem;
  background: rgba(255, 255, 255, 0.03);
  padding: 1rem;
  border-radius: var(--radius-md);
  border: 1px solid var(--border-glass);
}

.cred-icon {
  width: 24px;
  height: 24px;
  color: var(--primary);
  flex-shrink: 0;
}

.cred-text h4 {
  font-size: 0.95rem;
  margin-bottom: 0.2rem;
}

.cred-text p {
  font-size: 0.8rem;
  color: var(--text-muted);
}

/* ==========================================================================
   YOUTUBE VIDEOS SHOWCASE SECTION
   ========================================================================== */
.videos-section {
  position: relative;
  padding: 6rem 0;
}

.videos-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 2rem;
}

.video-card {
  display: flex;
  flex-direction: column;
  border-radius: var(--radius-lg);
  overflow: hidden;
  border: 1px solid var(--border-glass);
  transition: transform 0.3s ease, box-shadow 0.3s ease, border-color 0.3s ease;
}

.video-card:hover {
  transform: translateY(-5px);
  border-color: rgba(56, 189, 248, 0.4);
  box-shadow: 0 15px 35px rgba(0, 0, 0, 0.5), 0 0 25px rgba(56, 189, 248, 0.15);
}

.video-thumb-container {
  position: relative;
  width: 100%;
  aspect-ratio: 16 / 9;
  overflow: hidden;
  background: #000;
  cursor: pointer;
}

.video-thumb-img {
  width: 100%;
  height: 100%;
  object-fit: cover;
  transition: transform 0.5s ease;
}

.video-card:hover .video-thumb-img {
  transform: scale(1.06);
}

.video-play-overlay {
  position: absolute;
  inset: 0;
  background: rgba(15, 23, 42, 0.4);
  display: flex;
  align-items: center;
  justify-content: center;
  transition: background 0.3s ease;
}

.video-card:hover .video-play-overlay {
  background: rgba(15, 23, 42, 0.2);
}

.play-btn-pulse {
  width: 56px;
  height: 56px;
  border-radius: 50%;
  background: #ff0000;
  color: #fff;
  display: flex;
  align-items: center;
  justify-content: center;
  box-shadow: 0 0 20px rgba(255, 0, 0, 0.6);
  transition: transform 0.3s cubic-bezier(0.16, 1, 0.3, 1), box-shadow 0.3s ease;
}

.play-btn-pulse svg {
  margin-left: 2px;
}

.video-card:hover .play-btn-pulse {
  transform: scale(1.18);
  box-shadow: 0 0 30px rgba(255, 0, 0, 0.9);
}

.video-tag-badge {
  position: absolute;
  top: 1rem;
  left: 1rem;
  background: rgba(15, 23, 42, 0.88);
  backdrop-filter: blur(8px);
  -webkit-backdrop-filter: blur(8px);
  color: var(--primary);
  font-size: 0.75rem;
  font-weight: 700;
  padding: 0.3rem 0.65rem;
  border-radius: var(--radius-sm);
  border: 1px solid rgba(56, 189, 248, 0.35);
}

.video-type-badge {
  position: absolute;
  bottom: 0.75rem;
  right: 0.75rem;
  background: rgba(255, 0, 0, 0.9);
  color: #fff;
  font-size: 0.7rem;
  font-weight: 700;
  padding: 0.2rem 0.5rem;
  border-radius: 4px;
  letter-spacing: 0.04em;
  text-transform: uppercase;
}

.video-body {
  padding: 1.5rem;
  display: flex;
  flex-direction: column;
  flex-grow: 1;
}

.video-card-title {
  font-size: 1.15rem;
  font-weight: 700;
  color: #ffffff;
  margin-bottom: 0.65rem;
  line-height: 1.4;
}

.video-card-desc {
  font-size: 0.88rem;
  color: var(--text-muted);
  line-height: 1.6;
  margin-bottom: 1.5rem;
  flex-grow: 1;
}

.video-card-footer {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding-top: 1rem;
  border-top: 1px solid rgba(255, 255, 255, 0.06);
}

.btn-watch-video {
  display: inline-flex;
  align-items: center;
  gap: 0.45rem;
  background: linear-gradient(135deg, rgba(239, 68, 68, 0.2), rgba(220, 38, 38, 0.3));
  border: 1px solid rgba(239, 68, 68, 0.5);
  color: #ffffff;
  font-size: 0.85rem;
  font-weight: 600;
  padding: 0.5rem 1rem;
  border-radius: var(--radius-sm);
  cursor: pointer;
  transition: all 0.25s ease;
}

.btn-watch-video:hover {
  background: #ff0000;
  border-color: #ff0000;
  box-shadow: 0 0 16px rgba(255, 0, 0, 0.5);
  transform: translateY(-1px);
}

.yt-direct-link {
  display: inline-flex;
  align-items: center;
  gap: 0.35rem;
  color: var(--text-muted);
  font-size: 0.82rem;
  text-decoration: none;
  font-weight: 500;
  transition: color 0.2s ease;
}

.yt-direct-link:hover {
  color: var(--primary);
}

/* YouTube Channel Subscribe Banner */
.yt-channel-banner {
  margin-top: 3.5rem;
  background: linear-gradient(135deg, rgba(239, 68, 68, 0.08) 0%, rgba(15, 23, 42, 0.85) 100%);
  border: 1px solid rgba(239, 68, 68, 0.25);
  border-radius: var(--radius-lg);
  padding: 1.75rem 2.25rem;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1.5rem;
  flex-wrap: wrap;
  box-shadow: 0 10px 30px rgba(0, 0, 0, 0.4);
}

.yt-channel-info {
  display: flex;
  align-items: center;
  gap: 1.25rem;
}

.yt-logo-icon {
  width: 54px;
  height: 54px;
  border-radius: 14px;
  background: rgba(255, 0, 0, 0.12);
  border: 1px solid rgba(255, 0, 0, 0.3);
  display: flex;
  align-items: center;
  justify-content: center;
  flex-shrink: 0;
}

.yt-channel-title {
  font-size: 1.15rem;
  font-weight: 700;
  color: #fff;
  margin-bottom: 0.3rem;
}

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

.btn-yt-sub {
  background: linear-gradient(135deg, #ef4444 0%, #dc2626 100%);
  color: #fff;
  font-weight: 700;
  font-size: 0.95rem;
  padding: 0.85rem 1.6rem;
  border-radius: var(--radius-md);
  text-decoration: none;
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  box-shadow: 0 4px 20px rgba(239, 68, 68, 0.35);
  transition: all 0.3s ease;
}

.btn-yt-sub:hover {
  transform: translateY(-2px);
  box-shadow: 0 6px 28px rgba(239, 68, 68, 0.6);
  color: #fff;
}

/* ==========================================================================
   VIDEO LIGHTBOX MODAL
   ========================================================================== */
.video-modal-overlay {
  position: fixed;
  inset: 0;
  z-index: 10000;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 1.5rem;
  opacity: 0;
  visibility: hidden;
  transition: opacity 0.3s ease, visibility 0.3s ease;
}

.video-modal-overlay.active {
  opacity: 1;
  visibility: visible;
}

.video-modal-backdrop {
  position: absolute;
  inset: 0;
  background: rgba(0, 0, 0, 0.85);
  backdrop-filter: blur(10px);
  -webkit-backdrop-filter: blur(10px);
}

.video-modal-card {
  position: relative;
  z-index: 2;
  width: 100%;
  max-width: 820px;
  background: var(--bg-surface);
  border: 1px solid rgba(255, 255, 255, 0.15);
  border-radius: var(--radius-lg);
  box-shadow: 0 25px 60px rgba(0, 0, 0, 0.8);
  overflow: hidden;
  transform: scale(0.95);
  transition: transform 0.3s cubic-bezier(0.16, 1, 0.3, 1);
}

.video-modal-overlay.active .video-modal-card {
  transform: scale(1);
}

.video-modal-close {
  position: absolute;
  top: 1rem;
  right: 1rem;
  z-index: 10;
  width: 36px;
  height: 36px;
  border-radius: 50%;
  background: rgba(255, 255, 255, 0.1);
  border: 1px solid rgba(255, 255, 255, 0.15);
  color: #fff;
  display: flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  transition: all 0.2s ease;
}

.video-modal-close:hover {
  background: #ff0000;
  border-color: #ff0000;
  transform: scale(1.08);
}

.video-modal-header {
  padding: 1rem 1.5rem;
  border-bottom: 1px solid rgba(255, 255, 255, 0.08);
  display: flex;
  align-items: center;
  gap: 0.75rem;
  padding-right: 3.5rem;
}

.video-modal-badge {
  font-size: 0.72rem;
  font-weight: 700;
  color: #ff0000;
  background: rgba(255, 0, 0, 0.12);
  padding: 0.25rem 0.5rem;
  border-radius: 4px;
  text-transform: uppercase;
}

.video-modal-title {
  font-size: 1.05rem;
  font-weight: 700;
  color: #fff;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}

.video-iframe-wrapper {
  position: relative;
  width: 100%;
  padding-bottom: 56.25%; /* 16:9 Aspect Ratio */
  height: 0;
  background: #000;
}

.video-iframe-wrapper iframe {
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  border: 0;
}

/* ==========================================================================
   TESTIMONIALS & REVIEWS
   ========================================================================== */
.testimonials-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 2rem;
}

.testimonial-card {
  padding: 2rem;
  display: flex;
  flex-direction: column;
  justify-content: space-between;
}

.stars-row {
  display: flex;
  gap: 0.25rem;
  color: #f59e0b;
  margin-bottom: 1.25rem;
}

.testimonial-text {
  font-size: 0.95rem;
  color: #cbd5e1;
  line-height: 1.65;
  margin-bottom: 1.5rem;
  font-style: italic;
}

.author-info {
  display: flex;
  align-items: center;
  gap: 1rem;
  border-top: 1px solid rgba(255, 255, 255, 0.06);
  padding-top: 1.25rem;
}

.author-avatar {
  width: 44px;
  height: 44px;
  border-radius: 50%;
  background: var(--grad-primary);
  display: flex;
  align-items: center;
  justify-content: center;
  font-weight: 700;
  color: #07090e;
  font-size: 1rem;
}

.author-name {
  font-weight: 700;
  font-size: 0.95rem;
  color: #fff;
}

.author-tag {
  font-size: 0.8rem;
  color: var(--text-muted);
}

/* ==========================================================================
   FAQ SECTION
   ========================================================================== */
.faq-list {
  max-width: 840px;
  margin: 0 auto;
  display: flex;
  flex-direction: column;
  gap: 1rem;
}

/* ==========================================================================
   REGISTRATION CTA SECTION & MODAL
   ========================================================================== */
.cta-banner {
  background: linear-gradient(135deg, rgba(99, 102, 241, 0.2) 0%, rgba(0, 229, 255, 0.2) 100%);
  border: 1px solid rgba(0, 229, 255, 0.3);
  border-radius: var(--radius-lg);
  padding: 4rem 3rem;
  text-align: center;
  position: relative;
  overflow: hidden;
  box-shadow: 0 20px 60px rgba(0, 0, 0, 0.6);
}

.cta-banner h2 {
  font-size: clamp(2rem, 3.5vw, 2.8rem);
  margin-bottom: 1rem;
}

.cta-banner p {
  font-size: 1.15rem;
  color: #cbd5e1;
  max-width: 650px;
  margin: 0 auto 2.5rem auto;
}

/* Modal */
.modal-overlay {
  position: fixed;
  inset: 0;
  background: rgba(0, 0, 0, 0.8);
  backdrop-filter: blur(8px);
  -webkit-backdrop-filter: blur(8px);
  z-index: 2000;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 1.5rem;
  opacity: 0;
  visibility: hidden;
  transition: all var(--transition-normal);
}

.modal-overlay.active {
  opacity: 1;
  visibility: visible;
}

.modal-card {
  width: 100%;
  max-width: 580px;
  background: #0f172a;
  border: 1px solid rgba(0, 229, 255, 0.3);
  border-radius: var(--radius-lg);
  padding: 2.5rem;
  position: relative;
  box-shadow: 0 25px 60px rgba(0, 0, 0, 0.9), 0 0 40px rgba(0, 229, 255, 0.15);
  transform: translateY(20px) scale(0.95);
  transition: transform var(--transition-normal);
}

.modal-overlay.active .modal-card {
  transform: translateY(0) scale(1);
}

.modal-close-btn {
  position: absolute;
  top: 1.25rem;
  right: 1.25rem;
  background: rgba(255, 255, 255, 0.05);
  border: none;
  color: #fff;
  width: 36px;
  height: 36px;
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  transition: background var(--transition-fast);
}

.modal-close-btn:hover {
  background: rgba(255, 255, 255, 0.15);
  color: var(--primary);
}

.modal-header {
  margin-bottom: 2rem;
  text-align: center;
}

.modal-title {
  font-size: 1.75rem;
  margin-bottom: 0.5rem;
}

.modal-desc {
  font-size: 0.95rem;
  color: var(--text-muted);
}

.form-group {
  margin-bottom: 1.25rem;
}

.form-label {
  display: block;
  font-size: 0.9rem;
  font-weight: 600;
  color: #e2e8f0;
  margin-bottom: 0.5rem;
}

.form-input, .form-select, .form-textarea {
  width: 100%;
  padding: 0.85rem 1.1rem;
  background: rgba(15, 23, 42, 0.7);
  border: 1px solid var(--border-glass);
  border-radius: var(--radius-sm);
  color: #fff;
  font-family: var(--font-body);
  font-size: 0.95rem;
  outline: none;
  transition: border-color var(--transition-fast);
}

.form-input:focus, .form-select:focus, .form-textarea:focus {
  border-color: var(--primary);
  box-shadow: 0 0 10px rgba(0, 229, 255, 0.2);
}

.form-textarea {
  resize: vertical;
  min-height: 80px;
}

/* Floating Actions Bar */
.floating-contact-bar {
  position: fixed;
  bottom: 2rem;
  right: 2rem;
  display: flex;
  flex-direction: column;
  align-items: flex-end;
  gap: 0.85rem;
  z-index: 999;
}

.floating-pill-cta {
  display: inline-flex;
  align-items: center;
  gap: 0.6rem;
  background: var(--grad-primary);
  color: #07090e;
  font-family: var(--font-heading);
  font-weight: 700;
  font-size: 0.9rem;
  padding: 0.75rem 1.25rem;
  border-radius: var(--radius-full);
  border: none;
  cursor: pointer;
  box-shadow: 0 4px 20px var(--primary-glow);
  transition: all var(--transition-normal);
  white-space: nowrap;
}

.floating-pill-cta:hover {
  transform: translateY(-2px);
  box-shadow: 0 8px 30px rgba(0, 229, 255, 0.65);
  color: #000;
}

.pulsing-dot {
  width: 8px;
  height: 8px;
  border-radius: 50%;
  background: #07090e;
  animation: pulse-dot 1.5s infinite ease-in-out;
}

@keyframes pulse-dot {
  0%, 100% {
    transform: scale(1);
    opacity: 1;
  }
  50% {
    transform: scale(1.4);
    opacity: 0.5;
  }
}

.floating-icons-group {
  display: flex;
  flex-direction: column;
  gap: 0.75rem;
}

.floating-btn {
  width: 54px;
  height: 54px;
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  box-shadow: 0 8px 25px rgba(0, 0, 0, 0.5);
  color: #fff;
  text-decoration: none;
  transition: transform var(--transition-normal);
  position: relative;
}

.floating-btn:hover {
  transform: scale(1.1);
}

.floating-btn.btn-zalo {
  background: #0068ff;
}

.floating-btn.btn-hotline {
  background: #10b981;
}

.floating-tooltip {
  position: absolute;
  right: 65px;
  background: rgba(15, 23, 42, 0.95);
  color: #fff;
  padding: 0.35rem 0.75rem;
  border-radius: var(--radius-sm);
  font-size: 0.8rem;
  font-weight: 600;
  white-space: nowrap;
  pointer-events: none;
  opacity: 0;
  transform: translateX(10px);
  transition: all var(--transition-fast);
  border: 1px solid var(--border-glass);
}

.floating-btn:hover .floating-tooltip {
  opacity: 1;
  transform: translateX(0);
}

/* ==========================================================================
   FOOTER
   ========================================================================== */
.site-footer {
  background: #04060a;
  border-top: 1px solid var(--border-glass);
  padding: 4.5rem 0 2rem 0;
  position: relative;
}

.footer-grid {
  display: grid;
  grid-template-columns: 1.5fr 1fr 1fr 1.2fr;
  gap: 3rem;
  margin-bottom: 3.5rem;
}

.footer-col h4 {
  font-size: 1.05rem;
  margin-bottom: 1.25rem;
  color: #fff;
}

.footer-desc {
  font-size: 0.925rem;
  color: var(--text-muted);
  line-height: 1.6;
  margin-top: 1rem;
}

.footer-links {
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: 0.75rem;
}

.footer-links a {
  color: var(--text-muted);
  text-decoration: none;
  font-size: 0.925rem;
  transition: color var(--transition-fast);
}

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

.footer-contact-item {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  color: var(--text-muted);
  font-size: 0.925rem;
  margin-bottom: 0.75rem;
}

.footer-contact-item a {
  color: inherit;
  text-decoration: none;
  transition: color 0.2s ease;
}

.footer-contact-item a:hover {
  color: var(--primary);
  text-decoration: underline;
}

.footer-bottom {
  border-top: 1px solid rgba(255, 255, 255, 0.05);
  padding-top: 2rem;
  display: flex;
  justify-content: space-between;
  align-items: center;
  flex-wrap: wrap;
  gap: 1rem;
  font-size: 0.85rem;
  color: var(--text-dim);
}

/* ==========================================================================
   RESPONSIVE MEDIA QUERIES
   ========================================================================== */
@media (max-width: 1024px) {
  /* Navbar collapses to hamburger menu on tablet/iPad/small laptop */
  .nav-links, .nav-cta-group {
    display: none;
  }
  
  .mobile-toggle {
    display: block;
  }

  .hero-grid {
    grid-template-columns: 1fr;
    text-align: center;
    gap: 2.75rem;
  }
  
  .hero-desc {
    margin-left: auto;
    margin-right: auto;
  }
  
  .hero-actions {
    justify-content: center;
  }
  
  .hero-stats-row {
    justify-content: center;
  }
  
  .course-cards-grid {
    grid-template-columns: 1fr;
    max-width: 540px;
    margin: 0 auto;
  }
  
  .course-card.highlighted {
    transform: none;
  }

  .study-modes-grid {
    grid-template-columns: 1fr;
    max-width: 540px;
    margin: 0 auto;
  }
  
  .instructor-grid {
    grid-template-columns: 1fr;
    max-width: 600px;
    margin: 0 auto;
  }
  
  .testimonials-grid {
    grid-template-columns: 1fr;
    max-width: 540px;
    margin: 0 auto;
  }

  .videos-grid {
    grid-template-columns: 1fr;
    max-width: 580px;
    margin: 0 auto;
  }

  .yt-channel-banner {
    flex-direction: column;
    text-align: center;
    justify-content: center;
    padding: 1.5rem;
  }

  .yt-channel-info {
    flex-direction: column;
    text-align: center;
  }
  
  .footer-grid {
    grid-template-columns: 1fr 1fr;
    gap: 2.5rem;
  }
}

@media (max-width: 768px) {
  /* Global Layout */
  .container {
    padding: 0 1.15rem;
  }

  section {
    padding: 3.5rem 0;
  }

  .section-title {
    font-size: clamp(1.65rem, 6.5vw, 2.2rem);
    margin-bottom: 0.85rem;
  }

  .section-desc {
    font-size: 0.95rem;
    line-height: 1.6;
  }

  .section-header {
    margin-bottom: 2.25rem;
  }

  /* Header & Mobile Drawer */
  .navbar {
    height: 70px;
  }

  .navbar.scrolled {
    height: 65px;
  }

  .mobile-menu-drawer {
    display: flex;
    position: fixed;
    top: 70px;
    left: 0;
    width: 100%;
    max-height: calc(100vh - 70px);
    overflow-y: auto;
    -webkit-overflow-scrolling: touch;
    background: rgba(11, 15, 25, 0.98);
    backdrop-filter: blur(24px);
    -webkit-backdrop-filter: blur(24px);
    border-bottom: 1px solid var(--border-glass);
    padding: 1.5rem 1.25rem 2.5rem;
    flex-direction: column;
    gap: 1rem;
    transform: translateY(-100%);
    opacity: 0;
    visibility: hidden;
    transition: all var(--transition-normal);
    z-index: 1001;
  }
  
  .mobile-menu-drawer.open {
    transform: translateY(0);
    opacity: 1;
    visibility: visible;
  }

  .mobile-nav-link {
    font-size: 1rem;
    padding: 0.4rem 0;
    border-bottom: 1px solid rgba(255, 255, 255, 0.05);
  }

  .mobile-cta-btn {
    margin-top: 0.5rem;
    width: 100%;
    padding: 0.85rem;
  }

  /* Hero Section */
  .hero-section {
    padding-top: 95px;
    padding-bottom: 3rem;
    min-height: auto;
  }

  .hero-grid {
    gap: 2rem;
  }

  .hero-badge-wrap {
    margin-bottom: 1rem;
    padding: 0.35rem 0.85rem;
  }

  .hero-badge-text {
    font-size: 0.78rem;
  }

  .hero-title {
    font-size: clamp(1.85rem, 7vw, 2.45rem);
    line-height: 1.2;
    margin-bottom: 1rem;
  }

  .hero-desc {
    font-size: 0.95rem;
    line-height: 1.6;
    margin-bottom: 1.75rem;
  }

  .hero-actions {
    flex-direction: column;
    width: 100%;
    gap: 0.85rem;
    margin-bottom: 2rem;
  }

  .hero-actions .btn {
    width: 100%;
    padding: 0.9rem 1.5rem;
    font-size: 0.95rem;
  }

  .hero-stats-row {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 0.5rem;
    text-align: center;
    padding-top: 1.5rem;
  }

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

  .stat-num {
    font-size: 1.4rem;
  }

  .stat-label {
    font-size: 0.72rem;
    line-height: 1.3;
  }

  .hero-float-badge {
    position: static;
    margin-top: 1rem;
    border-radius: var(--radius-md);
  }

  /* Courses Cards */
  .course-cards-grid {
    gap: 1.75rem;
    max-width: 100%;
  }

  .course-image-thumb {
    height: 180px;
  }

  .course-body {
    padding: 1.35rem 1.15rem;
  }

  .course-title {
    font-size: 1.25rem;
  }

  .price-amount {
    font-size: 1.75rem;
  }

  .course-card-footer .btn {
    width: 100%;
  }

  /* Study Modes */
  .study-modes-grid {
    gap: 1.25rem;
    max-width: 100%;
  }

  .study-mode-card {
    padding: 1.5rem 1.15rem;
  }

  /* Syllabus */
  .syllabus-tab-controls {
    flex-direction: column;
    gap: 0.6rem;
    width: 100%;
    margin-bottom: 2rem;
  }

  .tab-btn {
    width: 100%;
    text-align: center;
    padding: 0.75rem 1rem;
    font-size: 0.88rem;
  }

  .accordion-list {
    gap: 0.75rem;
  }

  .accordion-header {
    padding: 0.95rem 1rem;
  }

  .acc-title-group {
    gap: 0.65rem;
  }

  .session-badge {
    font-size: 0.7rem;
    padding: 0.25rem 0.5rem;
  }

  .session-name {
    font-size: 0.92rem;
    line-height: 1.4;
  }

  .accordion-body {
    padding: 1rem;
    font-size: 0.88rem;
  }

  /* Comparison Matrix Table */
  .mobile-table-hint {
    display: flex;
  }

  .matrix-table {
    min-width: 620px;
  }

  .matrix-table th, .matrix-table td {
    padding: 0.85rem 0.95rem;
    font-size: 0.85rem;
  }

  .matrix-table th {
    font-size: 0.88rem;
  }

  /* Tuition Calculator */
  .calculator-box {
    padding: 1.5rem 1.15rem;
    border-radius: var(--radius-md);
  }

  .calc-options-grid {
    grid-template-columns: 1fr;
    gap: 1.25rem;
    margin-bottom: 1.5rem;
  }

  .calc-result-panel {
    flex-direction: column;
    align-items: stretch;
    gap: 1.25rem;
    padding-top: 1.5rem;
  }

  .calc-total-box {
    text-align: center;
  }

  .calc-total-val {
    font-size: 1.85rem;
  }

  .calc-result-panel .btn {
    width: 100%;
    justify-content: center;
  }

  /* Instructor Section */
  .instructor-grid {
    gap: 2rem;
    max-width: 100%;
  }

  .instructor-image-frame {
    max-width: 300px;
    margin: 0 auto;
  }

  .instructor-name {
    font-size: 1.55rem;
  }

  .instructor-badges-row {
    flex-direction: column;
    gap: 0.6rem;
  }

  .instructor-badge-item {
    width: 100%;
  }

  .instructor-cta-box {
    flex-direction: column;
    text-align: center;
    gap: 1rem;
    padding: 1.25rem;
  }

  .instructor-cta-box .btn {
    width: 100%;
    justify-content: center;
  }

  /* YouTube Videos Section */
  .videos-grid {
    grid-template-columns: 1fr;
    gap: 1.5rem;
    max-width: 100%;
  }

  .video-card-title {
    font-size: 1.05rem;
  }

  .video-body {
    padding: 1.25rem 1.1rem;
  }

  .yt-channel-banner {
    padding: 1.5rem 1.15rem;
    margin-top: 2rem;
    flex-direction: column;
    text-align: center;
  }

  .yt-channel-info {
    flex-direction: column;
    text-align: center;
    gap: 0.85rem;
  }

  .btn-yt-sub {
    width: 100%;
    justify-content: center;
  }

  /* Testimonials & FAQ */
  .testimonials-grid {
    grid-template-columns: 1fr;
    gap: 1.25rem;
    max-width: 100%;
  }

  .testimonial-card {
    padding: 1.35rem 1.15rem;
  }

  .faq-list {
    gap: 0.75rem;
  }

  /* Bottom CTA Banner */
  .cta-banner {
    padding: 2.25rem 1.15rem;
  }

  .cta-banner h2 {
    font-size: 1.65rem;
  }

  .cta-banner p {
    font-size: 0.95rem;
    margin-bottom: 1.75rem;
  }

  .cta-banner .btn {
    width: 100%;
    justify-content: center;
  }

  /* Modals */
  .modal-overlay, .video-modal-overlay {
    padding: 0.75rem;
  }

  .modal-card {
    padding: 1.6rem 1.15rem;
    max-height: 90vh;
    overflow-y: auto;
    width: 100%;
  }

  .modal-title {
    font-size: 1.25rem;
  }

  .modal-subtitle {
    font-size: 0.82rem;
    margin-bottom: 1.25rem;
  }

  .form-group {
    margin-bottom: 1rem;
  }

  .form-group label {
    font-size: 0.85rem;
  }

  .form-input {
    padding: 0.75rem 0.95rem;
    font-size: 0.9rem;
  }

  .modal-card .btn-primary {
    width: 100%;
    justify-content: center;
    padding: 0.85rem;
  }

  .video-modal-card {
    width: 100%;
    max-width: 100%;
  }

  .video-modal-header {
    padding: 0.75rem 1rem;
    padding-right: 3rem;
  }

  .video-modal-title {
    font-size: 0.92rem;
  }

  /* Floating Actions Bar on Mobile */
  /* Hide large floating pill on mobile so it doesn't block content */
  .floating-pill-cta {
    display: none !important;
  }

  .floating-contact-bar {
    bottom: 1.15rem;
    right: 1.15rem;
    gap: 0.65rem;
    z-index: 990; /* below mobile menu drawer (1001) */
  }

  .floating-btn {
    width: 48px;
    height: 48px;
  }

  .floating-btn svg {
    width: 22px;
    height: 22px;
  }

  .floating-tooltip {
    display: none;
  }

  /* Footer */
  .footer-grid {
    grid-template-columns: 1fr;
    gap: 2rem;
  }

  .footer-bottom {
    flex-direction: column;
    text-align: center;
    gap: 0.6rem;
  }
}