/* ==========================================================================
   Allen Kuo - Personal Landing Page & Online Courses
   Design System: Modern Professional Blue Palette & Clean Tech Aesthetics
   ========================================================================== */

/* --------------------------------------------------------------------------
   1. CSS Variables & Design Tokens
   -------------------------------------------------------------------------- */
:root {
  /* Color Palette - Tech Blues & Slate */
  --primary-50: #eff6ff;
  --primary-100: #dbeafe;
  --primary-200: #bfdbfe;
  --primary-300: #93c5fd;
  --primary-400: #60a5fa;
  --primary-500: #3b82f6;
  --primary-600: #2563eb; /* Core Brand Blue */
  --primary-700: #1d4ed8;
  --primary-800: #1e40af;
  --primary-900: #1e3a8a;
  --primary-950: #0b1329; /* Midnight Navy */

  --accent-cyan: #06b6d4;
  --accent-sky: #38bdf8;
  --accent-amber: #f59e0b;
  --accent-emerald: #10b981;

  /* Neutral Shades */
  --slate-50: #f8fafc;
  --slate-100: #f1f5f9;
  --slate-200: #e2e8f0;
  --slate-300: #cbd5e1;
  --slate-400: #94a3b8;
  --slate-500: #64748b;
  --slate-600: #475569;
  --slate-700: #334155;
  --slate-800: #1e293b;
  --slate-900: #0f172a;

  /* Backgrounds & Surfaces */
  --bg-main: #f8fafc;
  --bg-surface: #ffffff;
  --bg-surface-glass: rgba(255, 255, 255, 0.85);
  --bg-card: #ffffff;
  --bg-dark-section: #0b1329;
  --bg-dark-card: rgba(255, 255, 255, 0.05);

  /* Text Colors */
  --text-main: #0f172a;
  --text-muted: #64748b;
  --text-light: #94a3b8;
  --text-inverse: #ffffff;
  --text-inverse-muted: #cbd5e1;

  /* Gradients */
  --grad-primary: linear-gradient(135deg, #1d4ed8 0%, #2563eb 50%, #06b6d4 100%);
  --grad-subtle: linear-gradient(180deg, #eff6ff 0%, #ffffff 100%);
  --grad-hero: radial-gradient(circle at top center, rgba(37, 99, 235, 0.12) 0%, rgba(248, 250, 252, 0) 70%);
  --grad-dark-hero: radial-gradient(circle at top right, rgba(37, 99, 235, 0.25) 0%, rgba(11, 19, 41, 0.95) 75%);
  --grad-card-csharp: linear-gradient(135deg, #4338ca 0%, #2563eb 60%, #38bdf8 100%);
  --grad-card-oop: linear-gradient(135deg, #0369a1 0%, #0284c7 50%, #06b6d4 100%);
  --grad-badge: linear-gradient(135deg, #f59e0b 0%, #ea580c 100%);
  --grad-glow: radial-gradient(600px circle at var(--mouse-x, 50%) var(--mouse-y, 50%), rgba(37, 99, 235, 0.08), transparent 40%);

  /* Typography */
  --font-sans: 'Plus Jakarta Sans', 'Noto Sans TC', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
  --font-mono: 'JetBrains Mono', 'Fira Code', Consolas, monospace;

  /* Shadows */
  --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
  --shadow-md: 0 4px 6px -1px rgba(15, 23, 42, 0.08), 0 2px 4px -2px rgba(15, 23, 42, 0.04);
  --shadow-lg: 0 10px 15px -3px rgba(15, 23, 42, 0.08), 0 4px 6px -4px rgba(15, 23, 42, 0.03);
  --shadow-xl: 0 20px 25px -5px rgba(15, 23, 42, 0.1), 0 8px 10px -6px rgba(15, 23, 42, 0.04);
  --shadow-glow-blue: 0 0 25px rgba(37, 99, 235, 0.28);
  --shadow-card-hover: 0 25px 35px -10px rgba(37, 99, 235, 0.18);

  /* Radius */
  --radius-sm: 6px;
  --radius-md: 12px;
  --radius-lg: 18px;
  --radius-xl: 24px;
  --radius-full: 9999px;

  /* Transitions */
  --transition-fast: 0.18s ease;
  --transition-normal: 0.3s cubic-bezier(0.16, 1, 0.3, 1);
  --transition-smooth: 0.5s cubic-bezier(0.16, 1, 0.3, 1);

  /* Layout */
  --container-max-width: 1200px;
  --nav-height: 76px;
}

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

html {
  scroll-behavior: smooth;
  scroll-padding-top: calc(var(--nav-height) + 16px);
  -webkit-text-size-adjust: 100%;
}

body {
  font-family: var(--font-sans);
  font-size: 16px;
  line-height: 1.65;
  color: var(--text-main);
  background-color: var(--bg-main);
  overflow-x: hidden;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

a {
  color: inherit;
  text-decoration: none;
  transition: color var(--transition-fast);
}

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

ul, ol {
  list-style: none;
}

button, input, textarea {
  font-family: inherit;
  font-size: inherit;
  border: none;
  outline: none;
}

/* --------------------------------------------------------------------------
   3. Container & Utility Classes
   -------------------------------------------------------------------------- */
.container {
  width: 100%;
  max-width: var(--container-max-width);
  margin-left: auto;
  margin-right: auto;
  padding-left: 24px;
  padding-right: 24px;
}

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

.section {
  padding: 96px 0;
  position: relative;
}

.section-header {
  text-align: center;
  max-width: 720px;
  margin: 0 auto 56px auto;
}

.section-badge {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 6px 16px;
  background-color: var(--primary-50);
  border: 1px solid var(--primary-200);
  border-radius: var(--radius-full);
  color: var(--primary-700);
  font-size: 0.875rem;
  font-weight: 700;
  letter-spacing: 0.5px;
  margin-bottom: 16px;
  text-transform: uppercase;
}

.section-badge.badge-dark {
  background-color: rgba(37, 99, 235, 0.15);
  border-color: rgba(96, 165, 250, 0.3);
  color: var(--accent-sky);
}

.section-title {
  font-size: 2.35rem;
  font-weight: 800;
  letter-spacing: -0.02em;
  color: var(--text-main);
  line-height: 1.25;
  margin-bottom: 16px;
}

.section-subtitle {
  font-size: 1.1rem;
  color: var(--text-muted);
  line-height: 1.7;
}

/* Buttons */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 10px;
  padding: 13px 28px;
  border-radius: var(--radius-md);
  font-weight: 600;
  font-size: 1rem;
  cursor: pointer;
  transition: all var(--transition-normal);
  text-align: center;
  position: relative;
  overflow: hidden;
}

.btn-primary {
  background: var(--grad-primary);
  color: var(--text-inverse);
  box-shadow: 0 4px 14px rgba(37, 99, 235, 0.35);
}

.btn-primary:hover {
  transform: translateY(-2px);
  box-shadow: 0 8px 22px rgba(37, 99, 235, 0.45);
  filter: brightness(1.05);
}

.btn-secondary {
  background-color: #ffffff;
  color: var(--primary-700);
  border: 1.5px solid var(--primary-200);
  box-shadow: var(--shadow-sm);
}

.btn-secondary:hover {
  background-color: var(--primary-50);
  border-color: var(--primary-400);
  transform: translateY(-2px);
  box-shadow: var(--shadow-md);
}

.btn-outline-light {
  background-color: transparent;
  color: var(--text-inverse);
  border: 1.5px solid rgba(255, 255, 255, 0.25);
}

.btn-outline-light:hover {
  background-color: rgba(255, 255, 255, 0.1);
  border-color: rgba(255, 255, 255, 0.5);
  transform: translateY(-2px);
}

.btn-block {
  width: 100%;
}

.btn-sm {
  padding: 8px 18px;
  font-size: 0.875rem;
  border-radius: var(--radius-sm);
}

/* --------------------------------------------------------------------------
   4. Header & Navigation (Left Avatar Logo)
   -------------------------------------------------------------------------- */
.site-header {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  height: var(--nav-height);
  background-color: rgba(255, 255, 255, 0.9);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border-bottom: 1px solid rgba(226, 232, 240, 0.8);
  z-index: 1000;
  transition: all var(--transition-normal);
}

.site-header.scrolled {
  background-color: rgba(255, 255, 255, 0.96);
  box-shadow: var(--shadow-md);
  height: 68px;
}

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

/* Brand & Logo with Avatar */
.brand-logo {
  display: flex;
  align-items: center;
  gap: 14px;
  text-decoration: none;
}

.logo-avatar-wrapper {
  position: relative;
  width: 46px;
  height: 46px;
  border-radius: var(--radius-full);
  padding: 2px;
  /* background: var(--grad-primary); */
  /* box-shadow: 0 0 12px rgba(37, 99, 235, 0.3); */
  transition: transform var(--transition-normal);
  flex-shrink: 0;
}

.brand-logo:hover .logo-avatar-wrapper {
  transform: rotate(5deg) scale(1.05);
}

.logo-avatar {
  width: 100%;
  height: 100%;
  border-radius: var(--radius-full);
  object-fit: cover;
  background-color: #ffffff;
}

.brand-text {
  display: flex;
  flex-direction: column;
  margin-top:20px;
}

.brand-name {
  font-size: 1.15rem;
  font-weight: 800;
  color: var(--slate-900);
  line-height: 1.2;
  letter-spacing: -0.01em;
}

.brand-title {
  font-size: 0.75rem;
  color: var(--primary-600);
  font-weight: 600;
  letter-spacing: 0.3px;
}

/* Nav Menu */
.nav-menu {
  display: flex;
  align-items: center;
  gap: 32px;
}

.nav-link {
  font-size: 0.95rem;
  font-weight: 600;
  color: var(--slate-600);
  position: relative;
  padding: 6px 0;
  transition: color var(--transition-fast);
}

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

.nav-link:hover,
.nav-link.active {
  color: var(--primary-600);
}

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

.nav-actions {
  display: flex;
  align-items: center;
  gap: 16px;
}

/* Mobile Toggle */
.mobile-toggle {
  display: none;
  background: none;
  border: none;
  cursor: pointer;
  padding: 8px;
  color: var(--slate-800);
  font-size: 1.5rem;
}

/* --------------------------------------------------------------------------
   5. Hero Section
   -------------------------------------------------------------------------- */
.hero-section {
  padding-top: calc(var(--nav-height) + 54px);
  padding-bottom: 90px;
  background: var(--grad-hero);
  position: relative;
  overflow: hidden;
}

.hero-section::before {
  content: '';
  position: absolute;
  top: -100px;
  right: -100px;
  width: 500px;
  height: 500px;
  background: radial-gradient(circle, rgba(37, 99, 235, 0.15) 0%, rgba(255, 255, 255, 0) 70%);
  border-radius: 50%;
  pointer-events: none;
}

.hero-grid {
  display: grid;
  grid-template-columns: 1.15fr 0.85fr;
  align-items: center;
  gap: 48px;
}

.hero-content {
  max-width: 640px;
}

.hero-badge-pill {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  padding: 8px 18px;
  background: rgba(37, 99, 235, 0.08);
  border: 1px solid rgba(37, 99, 235, 0.2);
  border-radius: var(--radius-full);
  color: var(--primary-700);
  font-size: 0.9rem;
  font-weight: 700;
  margin-bottom: 24px;
  backdrop-filter: blur(8px);
}

.hero-badge-pill .pill-dot {
  width: 8px;
  height: 8px;
  background-color: var(--accent-cyan);
  border-radius: 50%;
  box-shadow: 0 0 8px var(--accent-cyan);
  animation: pulse-glow 2s infinite;
}

@keyframes pulse-glow {
  0%, 100% { opacity: 1; transform: scale(1); }
  50% { opacity: 0.5; transform: scale(1.3); }
}

.hero-title {
  font-size: 3.1rem;
  font-weight: 800;
  line-height: 1.2;
  color: var(--slate-900);
  letter-spacing: -0.025em;
  margin-bottom: 20px;
}

.hero-desc {
  font-size: 1.15rem;
  line-height: 1.8;
  color: var(--slate-600);
  margin-bottom: 36px;
}

.hero-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 16px;
  margin-bottom: 48px;
}

.hero-stats-row {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 20px;
  padding-top: 28px;
  border-top: 1px solid var(--slate-200);
}

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

.stat-number {
  font-size: 1.85rem;
  font-weight: 800;
  color: var(--primary-600);
  line-height: 1.1;
  font-family: var(--font-sans);
}

.stat-label {
  font-size: 0.85rem;
  font-weight: 600;
  color: var(--slate-500);
  margin-top: 4px;
}

/* Hero Visual / Code Card */
.hero-visual-wrapper {
  position: relative;
}

.hero-card-main {
  background: #ffffff;
  border-radius: var(--radius-xl);
  padding: 32px;
  box-shadow: 0 20px 40px -15px rgba(37, 99, 235, 0.15), 0 0 0 1px var(--slate-200);
  position: relative;
  overflow: hidden;
}

.hero-card-header {
  display: flex;
  align-items: center;
  gap: 16px;
  padding-bottom: 20px;
  border-bottom: 1px solid var(--slate-100);
  margin-bottom: 20px;
}

.hero-avatar-large {
  width: 68px;
  height: 68px;
  border-radius: var(--radius-full);
  padding: 3px;
  background: var(--grad-primary);
  box-shadow: var(--shadow-glow-blue);
  flex-shrink: 0;
}

.hero-avatar-large img {
  width: 100%;
  height: 100%;
  border-radius: var(--radius-full);
  object-fit: cover;
  background: white;
}

.hero-card-meta h4 {
  font-size: 1.25rem;
  font-weight: 800;
  color: var(--slate-900);
}

.hero-card-meta p {
  font-size: 0.875rem;
  color: var(--primary-600);
  font-weight: 600;
}

/* Code Preview Block */
.code-preview {
  background-color: var(--primary-950);
  border-radius: var(--radius-md);
  padding: 18px 20px;
  color: #e2e8f0;
  font-family: var(--font-mono);
  font-size: 0.85rem;
  line-height: 1.6;
  box-shadow: inset 0 2px 6px rgba(0,0,0,0.5);
  margin-bottom: 20px;
}

.code-keyword { color: #f43f5e; }
.code-class { color: #38bdf8; }
.code-string { color: #a3e635; }
.code-method { color: #fbbf24; }
.code-comment { color: #64748b; font-style: italic; }

.tech-tags-list {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
}

.tech-tag {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 6px 12px;
  background-color: var(--primary-50);
  color: var(--primary-700);
  border-radius: var(--radius-sm);
  font-size: 0.8rem;
  font-weight: 700;
  border: 1px solid var(--primary-100);
}

.tech-tag i {
  color: var(--primary-600);
}

/* Floating Badges */
.floating-badge {
  position: absolute;
  padding: 12px 18px;
  background: #ffffff;
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-xl);
  border: 1px solid var(--slate-100);
  display: flex;
  align-items: center;
  gap: 12px;
  z-index: 2;
  animation: float-slow 4s ease-in-out infinite;
}

.floating-badge-1 {
  top: -20px;
  right: -15px;
}

.floating-badge-2 {
  bottom: -50px;
  left: -20px;
  animation-delay: 2s;
}

.floating-badge .badge-icon {
  width: 40px;
  height: 40px;
  border-radius: var(--radius-md);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.2rem;
}

.badge-icon.icon-blue {
  background: rgba(37, 99, 235, 0.1);
  color: var(--primary-600);
}

.badge-icon.icon-amber {
  background: rgba(245, 158, 11, 0.1);
  color: var(--accent-amber);
}

.floating-badge .badge-text strong {
  display: block;
  font-size: 0.9rem;
  color: var(--slate-900);
}

.floating-badge .badge-text span {
  font-size: 0.75rem;
  color: var(--slate-500);
}

@keyframes float-slow {
  0%, 100% { transform: translateY(0); }
  50% { transform: translateY(-8px); }
}

/* --------------------------------------------------------------------------
   6. About & Core Expertise Section
   -------------------------------------------------------------------------- */
.about-section {
  background-color: #ffffff;
  border-top: 1px solid var(--slate-200);
  border-bottom: 1px solid var(--slate-200);
}

.about-intro-box {
  background: var(--grad-subtle);
  border: 1px solid var(--primary-100);
  border-radius: var(--radius-xl);
  padding: 40px;
  margin-bottom: 64px;
  display: grid;
  grid-template-columns: auto 1fr;
  gap: 36px;
  align-items: center;
}

.about-avatar-frame {
  width: 140px;
  height: 140px;
  border-radius: var(--radius-xl);
  padding: 4px;
  background: var(--grad-primary);
  box-shadow: 0 10px 25px rgba(37, 99, 235, 0.2);
  flex-shrink: 0;
}

.about-avatar-frame img {
  width: 100%;
  height: 100%;
  border-radius: calc(var(--radius-xl) - 4px);
  object-fit: cover;
  background: white;
}

.about-intro-text h3 {
  font-size: 1.5rem;
  font-weight: 800;
  color: var(--slate-900);
  margin-bottom: 12px;
}

.about-intro-text p {
  color: var(--slate-600);
  line-height: 1.8;
  font-size: 1.05rem;
}

/* Expertise Cards Grid (4 Core Pillars) */
.expertise-grid {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 24px;
}

.expertise-card {
  background: #ffffff;
  border: 1px solid var(--slate-200);
  border-radius: var(--radius-lg);
  padding: 30px 24px;
  transition: all var(--transition-normal);
  display: flex;
  flex-direction: column;
  position: relative;
  overflow: hidden;
}

.expertise-card::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  height: 4px;
  background: var(--grad-primary);
  opacity: 0;
  transition: opacity var(--transition-fast);
}

.expertise-card:hover {
  transform: translateY(-6px);
  box-shadow: var(--shadow-xl);
  border-color: var(--primary-300);
}

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

.expertise-icon {
  width: 56px;
  height: 56px;
  border-radius: var(--radius-md);
  background: var(--primary-50);
  color: var(--primary-600);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.6rem;
  margin-bottom: 20px;
  transition: all var(--transition-normal);
}

.expertise-card:hover .expertise-icon {
  background: var(--primary-600);
  color: #ffffff;
  transform: scale(1.05);
}

.expertise-card h4 {
  font-size: 1.2rem;
  font-weight: 700;
  color: var(--slate-900);
  margin-bottom: 12px;
}

.expertise-card p {
  font-size: 0.92rem;
  color: var(--slate-500);
  line-height: 1.65;
  margin-bottom: 16px;
  flex-grow: 1;
}

.expertise-pill-list {
  display: flex;
  flex-wrap: wrap;
  gap: 6px;
}

.expertise-pill {
  font-size: 0.75rem;
  padding: 3px 8px;
  border-radius: 4px;
  background: var(--slate-100);
  color: var(--slate-600);
  font-weight: 600;
}

/* --------------------------------------------------------------------------
   7. Courses Showcase Section (Core Featured Cards)
   -------------------------------------------------------------------------- */
.courses-section {
  background-color: var(--slate-50);
  position: relative;
}

.courses-grid {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 36px;
  margin-bottom: 48px;
}

.course-card {
  background: #ffffff;
  border-radius: var(--radius-xl);
  border: 1px solid var(--slate-200);
  box-shadow: var(--shadow-lg);
  overflow: hidden;
  display: flex;
  flex-direction: column;
  transition: all var(--transition-normal);
  position: relative;
}

.course-card:hover {
  transform: translateY(-8px);
  box-shadow: var(--shadow-card-hover);
  border-color: var(--primary-400);
}

/* Course Visual Header */
.course-card-banner {
  height: 180px;
  position: relative;
  padding: 24px;
  display: flex;
  flex-direction: column;
  justify-content: space-between;
  color: #ffffff;
  overflow: hidden;
}

.banner-csharp {
  background: var(--grad-card-csharp);
}

.banner-oop {
  background: var(--grad-card-oop);
}

.banner-pattern {
  position: absolute;
  top: 0;
  right: 0;
  bottom: 0;
  left: 0;
  background-image: radial-gradient(rgba(255, 255, 255, 0.15) 1px, transparent 1px);
  background-size: 16px 16px;
  opacity: 0.6;
}

.course-card-banner .course-badge {
  align-self: flex-start;
  background: rgba(0, 0, 0, 0.35);
  backdrop-filter: blur(8px);
  padding: 5px 14px;
  border-radius: var(--radius-full);
  font-size: 0.8rem;
  font-weight: 700;
  letter-spacing: 0.5px;
  border: 1px solid rgba(255, 255, 255, 0.25);
  display: inline-flex;
  align-items: center;
  gap: 6px;
  z-index: 1;
}

.course-badge.badge-featured {
  background: var(--grad-badge);
  border-color: transparent;
}

.course-icon-symbol {
  font-size: 3.5rem;
  position: absolute;
  right: 20px;
  bottom: 10px;
  opacity: 0.22;
  font-weight: 900;
  font-family: var(--font-mono);
  user-select: none;
}

.banner-title-area {
  z-index: 1;
}

.banner-title-area h3 {
  font-size: 1.7rem;
  font-weight: 800;
  color: #ffffff;
  text-shadow: 0 2px 4px rgba(0,0,0,0.2);
}

/* Course Body */
.course-card-body {
  padding: 32px;
  display: flex;
  flex-direction: column;
  flex-grow: 1;
}

.course-desc {
  color: var(--slate-600);
  font-size: 1rem;
  line-height: 1.7;
  margin-bottom: 24px;
}

.course-features-title {
  font-size: 0.9rem;
  font-weight: 700;
  color: var(--slate-800);
  text-transform: uppercase;
  letter-spacing: 0.5px;
  margin-bottom: 12px;
}

.course-feature-list {
  display: flex;
  flex-direction: column;
  gap: 12px;
  margin-bottom: 28px;
}

.course-feature-item {
  display: flex;
  align-items: flex-start;
  gap: 10px;
  font-size: 0.92rem;
  color: var(--slate-700);
}

.course-feature-item i {
  color: var(--primary-600);
  margin-top: 3px;
  font-size: 0.95rem;
}

/* Pricing and Action */
.course-card-footer {
  margin-top: auto;
  padding-top: 24px;
  border-top: 1px solid var(--slate-200);
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
}

.course-price-wrap {
  display: flex;
  flex-direction: column;
}

.price-original {
  font-size: 0.85rem;
  color: var(--slate-400);
  text-decoration: line-through;
}

.price-current {
  display: flex;
  align-items: baseline;
  gap: 4px;
}

.price-currency {
  font-size: 1rem;
  font-weight: 700;
  color: var(--slate-900);
}

.price-amount {
  font-size: 1.85rem;
  font-weight: 800;
  color: var(--primary-600);
  line-height: 1;
}

/* Upcoming Course Teaser */
.upcoming-courses-banner {
  background: #ffffff;
  border: 1.5px dashed var(--primary-300);
  border-radius: var(--radius-lg);
  padding: 24px 32px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 20px;
}

.upcoming-info {
  display: flex;
  align-items: center;
  gap: 16px;
}

.upcoming-icon {
  width: 48px;
  height: 48px;
  border-radius: 50%;
  background: var(--primary-50);
  color: var(--primary-600);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.3rem;
  flex-shrink: 0;
}

.upcoming-info h4 {
  font-size: 1.1rem;
  font-weight: 700;
  color: var(--slate-900);
}

.upcoming-info p {
  font-size: 0.9rem;
  color: var(--slate-500);
}

/* --------------------------------------------------------------------------
   8. Why Choose Me / Teaching Philosophy
   -------------------------------------------------------------------------- */
.why-us-section {
  background-color: var(--bg-dark-section);
  color: var(--text-inverse);
  position: relative;
  overflow: hidden;
}

.why-us-section::before {
  content: '';
  position: absolute;
  top: 0;
  right: 0;
  width: 600px;
  height: 600px;
  background: radial-gradient(circle, rgba(37, 99, 235, 0.2) 0%, transparent 70%);
  pointer-events: none;
}

.why-us-section .section-title {
  color: var(--text-inverse);
}

.why-us-section .section-subtitle {
  color: var(--text-inverse-muted);
}

.values-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 28px;
}

.value-card {
  background: var(--bg-dark-card);
  border: 1px solid rgba(255, 255, 255, 0.08);
  border-radius: var(--radius-lg);
  padding: 36px 28px;
  transition: all var(--transition-normal);
  backdrop-filter: blur(10px);
}

.value-card:hover {
  background: rgba(255, 255, 255, 0.09);
  transform: translateY(-6px);
  border-color: rgba(96, 165, 250, 0.4);
}

.value-icon-box {
  width: 52px;
  height: 52px;
  border-radius: var(--radius-md);
  background: var(--grad-primary);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.4rem;
  color: #ffffff;
  margin-bottom: 22px;
  box-shadow: 0 4px 12px rgba(37, 99, 235, 0.4);
}

.value-card h4 {
  font-size: 1.25rem;
  font-weight: 700;
  margin-bottom: 12px;
  color: #ffffff;
}

.value-card p {
  color: var(--slate-300);
  font-size: 0.95rem;
  line-height: 1.7;
}

/* --------------------------------------------------------------------------
   9. CTA & Contact Section
   -------------------------------------------------------------------------- */
.cta-section {
  background: var(--grad-subtle);
  position: relative;
}

.cta-box {
  background: #ffffff;
  border: 1px solid var(--slate-200);
  border-radius: var(--radius-xl);
  padding: 60px 48px;
  box-shadow: var(--shadow-xl);
  display: grid;
  grid-template-columns: 1.2fr 0.8fr;
  gap: 48px;
  align-items: center;
}

.cta-text h2 {
  font-size: 2.2rem;
  font-weight: 800;
  color: var(--slate-900);
  margin-bottom: 16px;
  line-height: 1.25;
}

.cta-text p {
  font-size: 1.05rem;
  color: var(--slate-600);
  line-height: 1.75;
  margin-bottom: 28px;
}

.cta-contact-links {
  display: flex;
  flex-direction: column;
  gap: 16px;
}

.contact-card {
  display: flex;
  align-items: center;
  gap: 16px;
  padding: 16px 20px;
  background-color: var(--slate-50);
  border: 1px solid var(--slate-200);
  border-radius: var(--radius-md);
  transition: all var(--transition-normal);
}

.contact-card:hover {
  background-color: var(--primary-50);
  border-color: var(--primary-300);
  transform: translateX(4px);
}

.contact-icon {
  width: 42px;
  height: 42px;
  border-radius: 50%;
  background: var(--primary-600);
  color: #ffffff;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.1rem;
  flex-shrink: 0;
}

.contact-detail strong {
  display: block;
  font-size: 0.9rem;
  color: var(--slate-900);
}

.contact-detail span {
  font-size: 0.85rem;
  color: var(--slate-500);
}

/* --------------------------------------------------------------------------
   10. Footer
   -------------------------------------------------------------------------- */
.site-footer {
  background-color: var(--slate-900);
  color: var(--slate-400);
  padding: 60px 0 30px 0;
  border-top: 1px solid var(--slate-800);
}

.footer-grid {
  display: grid;
  grid-template-columns: 1.5fr 1fr 1fr;
  gap: 48px;
  margin-bottom: 48px;
}

.footer-brand .brand-name {
  color: #ffffff;
}

.footer-brand p {
  font-size: 0.9rem;
  line-height: 1.7;
  margin: 16px 0 20px 0;
  max-width: 360px;
}

.footer-socials {
  display: flex;
  gap: 12px;
}

.social-btn {
  width: 38px;
  height: 38px;
  border-radius: 50%;
  background: var(--slate-800);
  color: var(--slate-300);
  display: flex;
  align-items: center;
  justify-content: center;
  transition: all var(--transition-fast);
}

.social-btn:hover {
  background: var(--primary-600);
  color: #ffffff;
  transform: translateY(-3px);
}

.footer-col h5 {
  font-size: 1rem;
  font-weight: 700;
  color: #ffffff;
  margin-bottom: 20px;
}

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

.footer-links-list a {
  font-size: 0.9rem;
  color: var(--slate-400);
  transition: color var(--transition-fast);
}

.footer-links-list a:hover {
  color: var(--primary-400);
  padding-left: 4px;
}

.footer-bottom {
  padding-top: 28px;
  border-top: 1px solid var(--slate-800);
  display: flex;
  align-items: center;
  justify-content: space-between;
  font-size: 0.85rem;
}

/* --------------------------------------------------------------------------
   11. Back to top button & Scroll Animations
   -------------------------------------------------------------------------- */
.back-to-top {
  position: fixed;
  bottom: 28px;
  right: 28px;
  width: 44px;
  height: 44px;
  border-radius: 50%;
  background: var(--primary-600);
  color: #ffffff;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.1rem;
  box-shadow: 0 4px 14px rgba(37, 99, 235, 0.4);
  cursor: pointer;
  opacity: 0;
  visibility: hidden;
  transform: translateY(12px);
  transition: all var(--transition-normal);
  z-index: 999;
}

.back-to-top.visible {
  opacity: 1;
  visibility: visible;
  transform: translateY(0);
}

.back-to-top:hover {
  background: var(--primary-700);
  transform: translateY(-4px);
}

/* Scroll reveal utility */
.reveal-item {
  opacity: 0;
  transform: translateY(24px);
  transition: opacity 0.6s cubic-bezier(0.16, 1, 0.3, 1), transform 0.6s cubic-bezier(0.16, 1, 0.3, 1);
}

.reveal-item.revealed {
  opacity: 1;
  transform: translateY(0);
}

/* --------------------------------------------------------------------------
   12. Responsive Design (RWD Media Queries)
   -------------------------------------------------------------------------- */
@media (max-width: 1024px) {
  .hero-grid {
    grid-template-columns: 1fr;
    gap: 48px;
  }

  .hero-content {
    max-width: 100%;
    text-align: center;
  }

  .hero-actions {
    justify-content: center;
  }

  .hero-stats-row {
    max-width: 500px;
    margin: 0 auto;
  }

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

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

  .cta-box {
    grid-template-columns: 1fr;
    padding: 40px 32px;
  }
}

@media (max-width: 768px) {
  :root {
    --nav-height: 68px;
  }

  .mobile-toggle {
    display: block;
  }

  .nav-menu {
    position: fixed;
    top: var(--nav-height);
    left: 0;
    right: 0;
    background-color: #ffffff;
    flex-direction: column;
    padding: 28px 24px;
    gap: 20px;
    border-bottom: 1px solid var(--slate-200);
    box-shadow: var(--shadow-xl);
    transform: translateY(-120%);
    opacity: 0;
    pointer-events: none;
    transition: all var(--transition-normal);
  }

  .nav-menu.open {
    transform: translateY(0);
    opacity: 1;
    pointer-events: auto;
  }

  .nav-actions .btn {
    display: none;
  }

  .hero-title {
    font-size: 2.2rem;
  }

  .courses-grid {
    grid-template-columns: 1fr;
  }

  .about-intro-box {
    grid-template-columns: 1fr;
    text-align: center;
    padding: 30px 20px;
  }

  .about-avatar-frame {
    margin: 0 auto;
  }

  .expertise-grid {
    grid-template-columns: 1fr;
  }

  .values-grid {
    grid-template-columns: 1fr;
  }

  .footer-grid {
    grid-template-columns: 1fr;
    gap: 32px;
  }

  .footer-bottom {
    flex-direction: column;
    gap: 12px;
    text-align: center;
  }

  .floating-badge {
    display: none;
  }

  .upcoming-courses-banner {
    flex-direction: column;
    text-align: center;
  }

  .upcoming-info {
    flex-direction: column;
  }
}

@media (max-width: 480px) {
  .hero-title {
    font-size: 1.85rem;
  }

  .hero-actions .btn {
    width: 100%;
  }

  .hero-stats-row {
    grid-template-columns: 1fr;
    gap: 16px;
    text-align: center;
  }

  .course-card-footer {
    flex-direction: column;
    align-items: stretch;
  }

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