:root {
  --font-sans: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  --font-mono: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, "Liberation Mono", monospace;
  
  --bg: #090d16;
  --bg-surface: #101726;
  --bg-card: #151e32;
  --border: #232f48;
  --border-subtle: #1a2336;
  
  --primary: #6366f1;
  --primary-glow: rgba(99, 102, 241, 0.25);
  --primary-light: #818cf8;
  --accent: #f43f5e;
  --accent-glow: rgba(244, 63, 94, 0.25);
  --emerald: #10b981;
  
  --text-main: #f8fafc;
  --text-muted: #94a3b8;
  --text-dim: #64748b;
  
  --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
  --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -2px rgba(0, 0, 0, 0.1);
  --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.2), 0 4px 6px -4px rgba(0, 0, 0, 0.1);
  --shadow-glow: 0 0 30px -5px var(--primary-glow);
  
  --radius-sm: 8px;
  --radius-md: 14px;
  --radius-lg: 20px;
  --radius-xl: 28px;
}

@media (prefers-color-scheme: light) {
  :root {
    --bg: #f8fafc;
    --bg-surface: #ffffff;
    --bg-card: #f1f5f9;
    --border: #e2e8f0;
    --border-subtle: #edf2f7;
    
    --text-main: #0f172a;
    --text-muted: #475569;
    --text-dim: #94a3b8;
    
    --primary-glow: rgba(99, 102, 241, 0.15);
    --shadow-glow: 0 10px 25px -5px rgba(99, 102, 241, 0.15);
  }
}

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

html {
  font-family: var(--font-sans);
  color-scheme: dark light;
  background-color: var(--bg);
  color: var(--text-main);
  scroll-behavior: smooth;
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
}

body {
  min-height: 100vh;
  overflow-x: hidden;
  position: relative;
}

/* Atmospheric Background Glows */
.bg-glow-1 {
  position: absolute;
  top: -100px;
  left: 50%;
  transform: translateX(-50%);
  width: min(1000px, 90vw);
  height: 600px;
  background: radial-gradient(ellipse at center, var(--primary-glow) 0%, rgba(99, 102, 241, 0) 70%);
  pointer-events: none;
  z-index: 0;
}

.bg-glow-2 {
  position: absolute;
  top: 1400px;
  right: -200px;
  width: 800px;
  height: 600px;
  background: radial-gradient(ellipse at center, var(--accent-glow) 0%, rgba(244, 63, 94, 0) 70%);
  pointer-events: none;
  z-index: 0;
}

/* Container */
.container {
  width: min(1200px, 92%);
  margin: 0 auto;
  position: relative;
  z-index: 1;
}

/* Header & Nav */
header {
  position: sticky;
  top: 0;
  z-index: 100;
  backdrop-filter: blur(16px);
  -webkit-backdrop-filter: blur(16px);
  background: color-mix(in srgb, var(--bg) 80%, transparent);
  border-bottom: 1px solid var(--border-subtle);
  transition: all 0.3s ease;
}

.nav-wrapper {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 72px;
}

.brand {
  display: flex;
  align-items: center;
  gap: 12px;
  text-decoration: none;
  color: var(--text-main);
  font-weight: 800;
  font-size: 1.25rem;
}

.brand-icon {
  width: 40px;
  height: 40px;
  border-radius: 10px;
  display: flex;
  align-items: center;
  justify-content: center;
  background: linear-gradient(135deg, #6366f1, #a855f7);
  color: white;
  font-size: 1.25rem;
  box-shadow: 0 4px 12px var(--primary-glow);
}

.nav-links {
  display: flex;
  align-items: center;
  gap: 32px;
  list-style: none;
}

.nav-links a {
  text-decoration: none;
  color: var(--text-muted);
  font-weight: 500;
  font-size: 0.95rem;
  transition: color 0.2s ease;
}

.nav-links a:hover {
  color: var(--text-main);
}

/* Buttons */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 10px;
  padding: 12px 24px;
  border-radius: 12px;
  font-weight: 600;
  font-size: 0.95rem;
  text-decoration: none;
  transition: all 0.2s cubic-bezier(0.4, 0, 0.2, 1);
  cursor: pointer;
  border: 1px solid transparent;
}

.btn-playstore {
  background: #0f172a;
  color: #ffffff;
  border: 1px solid #334155;
  box-shadow: 0 4px 14px rgba(0, 0, 0, 0.3);
}

.btn-playstore:hover {
  background: #1e293b;
  border-color: #475569;
  transform: translateY(-2px);
  box-shadow: 0 6px 20px rgba(0, 0, 0, 0.4);
}

.btn-primary {
  background: linear-gradient(135deg, #4f46e5, #6366f1);
  color: white;
  box-shadow: 0 4px 14px var(--primary-glow);
}

.btn-primary:hover {
  background: linear-gradient(135deg, #4338ca, #4f46e5);
  transform: translateY(-2px);
  box-shadow: 0 8px 25px var(--primary-glow);
}

.btn-secondary {
  background: var(--bg-surface);
  color: var(--text-main);
  border: 1px solid var(--border);
}

.btn-secondary:hover {
  background: var(--bg-card);
  border-color: var(--primary);
  transform: translateY(-2px);
}

/* Hero Section */
.hero {
  padding: 80px 0 60px;
  text-align: center;
}

.badge {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 6px 16px;
  background: color-mix(in srgb, var(--primary) 12%, transparent);
  border: 1px solid color-mix(in srgb, var(--primary) 25%, transparent);
  border-radius: 100px;
  font-size: 0.85rem;
  font-weight: 600;
  color: var(--primary-light);
  margin-bottom: 24px;
}

.badge-pulse {
  width: 8px;
  height: 8px;
  border-radius: 50%;
  background-color: var(--emerald);
  box-shadow: 0 0 8px var(--emerald);
}

.hero h1 {
  font-size: clamp(2.4rem, 5.5vw, 4rem);
  font-weight: 800;
  line-height: 1.15;
  letter-spacing: -0.03em;
  margin-bottom: 24px;
  text-wrap: balance;
}

.gradient-text {
  background: linear-gradient(135deg, #818cf8 0%, #c084fc 50%, #fb7185 100%);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
}

.hero-subtitle {
  font-size: clamp(1.05rem, 2vw, 1.25rem);
  color: var(--text-muted);
  max-width: 680px;
  margin: 0 auto 36px;
  text-wrap: pretty;
}

.hero-actions {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 16px;
  flex-wrap: wrap;
  margin-bottom: 50px;
}

/* App Mockup Preview */
.mockup-container {
  max-width: 420px;
  margin: 0 auto;
  perspective: 1000px;
}

.phone-frame {
  background: #0f172a;
  border: 8px solid #1e293b;
  border-radius: 44px;
  overflow: hidden;
  box-shadow: 0 25px 50px -12px rgba(0, 0, 0, 0.5), 0 0 40px var(--primary-glow);
  position: relative;
  text-align: left;
}

.phone-notch {
  width: 120px;
  height: 20px;
  background: #1e293b;
  margin: 0 auto 12px;
  border-bottom-left-radius: 12px;
  border-bottom-right-radius: 12px;
}

.phone-content {
  padding: 12px 18px 24px;
  background: #090d16;
}

.mockup-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: 16px;
  padding-bottom: 12px;
  border-bottom: 1px solid #1e293b;
}

.mockup-sensei {
  display: flex;
  align-items: center;
  gap: 8px;
}

.sensei-avatar {
  width: 32px;
  height: 32px;
  border-radius: 50%;
  background: #6366f1;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 14px;
}

.sensei-name {
  font-size: 0.85rem;
  font-weight: 700;
  color: #f8fafc;
}

.sensei-role {
  font-size: 0.7rem;
  color: #94a3b8;
}

.mockup-session-badge {
  font-size: 0.7rem;
  padding: 3px 8px;
  border-radius: 100px;
  background: rgba(16, 185, 129, 0.15);
  color: #34d399;
  border: 1px solid rgba(16, 185, 129, 0.3);
  font-weight: 600;
}

.transcript-bubble {
  background: #151e32;
  border: 1px solid #232f48;
  border-radius: 18px;
  padding: 14px;
  margin-bottom: 14px;
}

.transcript-ja {
  font-size: 1.15rem;
  font-weight: 700;
  color: #ffffff;
  margin-bottom: 4px;
}

.transcript-ro {
  font-size: 0.82rem;
  font-family: var(--font-mono);
  color: #818cf8;
  margin-bottom: 6px;
}

.transcript-en {
  font-size: 0.82rem;
  color: #94a3b8;
}

.transcript-user {
  background: #1e1b4b;
  border-color: #3730a3;
  text-align: right;
}

.mockup-mic-bar {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 12px;
  padding-top: 10px;
}

.waveform-bar {
  width: 4px;
  height: 24px;
  background: #6366f1;
  border-radius: 2px;
  animation: wave 1s ease-in-out infinite alternate;
}
.waveform-bar:nth-child(2) { height: 36px; animation-delay: 0.2s; }
.waveform-bar:nth-child(3) { height: 18px; animation-delay: 0.4s; }
.waveform-bar:nth-child(4) { height: 30px; animation-delay: 0.1s; }
.waveform-bar:nth-child(5) { height: 20px; animation-delay: 0.3s; }

@keyframes wave {
  0% { transform: scaleY(0.4); }
  100% { transform: scaleY(1.1); }
}

/* Features Section */
.features {
  padding: 100px 0;
}

.section-header {
  text-align: center;
  margin-bottom: 60px;
}

.section-tag {
  color: var(--primary-light);
  font-weight: 700;
  font-size: 0.85rem;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  margin-bottom: 12px;
}

.section-title {
  font-size: clamp(2rem, 3.5vw, 2.75rem);
  font-weight: 800;
  letter-spacing: -0.02em;
  margin-bottom: 16px;
}

.section-desc {
  color: var(--text-muted);
  max-width: 620px;
  margin: 0 auto;
}

.grid-3 {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(320px, 1fr));
  gap: 24px;
}

.card {
  background: var(--bg-surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 32px;
  transition: all 0.3s ease;
  position: relative;
  overflow: hidden;
}

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

.card-icon {
  width: 48px;
  height: 48px;
  border-radius: var(--radius-md);
  background: color-mix(in srgb, var(--primary) 15%, transparent);
  color: var(--primary-light);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.5rem;
  margin-bottom: 20px;
}

.card h3 {
  font-size: 1.25rem;
  font-weight: 700;
  margin-bottom: 12px;
}

.card p {
  color: var(--text-muted);
  font-size: 0.95rem;
  line-height: 1.6;
}

/* Tutors Grid */
.tutors {
  padding: 80px 0;
  background: var(--bg-surface);
  border-top: 1px solid var(--border-subtle);
  border-bottom: 1px solid var(--border-subtle);
}

.tutor-card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius-md);
  padding: 24px;
  display: flex;
  align-items: flex-start;
  gap: 16px;
  transition: transform 0.2s ease, border-color 0.2s ease;
}

.tutor-card:hover {
  transform: translateY(-2px);
  border-color: var(--primary);
}

.tutor-avatar {
  width: 48px;
  height: 48px;
  border-radius: 12px;
  background: linear-gradient(135deg, var(--primary), var(--accent));
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.3rem;
  color: white;
  shrink: 0;
}

.tutor-info h4 {
  font-size: 1.05rem;
  font-weight: 700;
  margin-bottom: 4px;
}

.tutor-tag {
  display: inline-block;
  font-size: 0.75rem;
  font-weight: 600;
  color: var(--primary-light);
  margin-bottom: 6px;
}

.tutor-desc {
  font-size: 0.85rem;
  color: var(--text-muted);
}

/* CTA Banner */
.cta-banner {
  padding: 100px 0;
  text-align: center;
}

.cta-box {
  background: linear-gradient(135deg, color-mix(in srgb, var(--primary) 20%, var(--bg-surface)), var(--bg-surface));
  border: 1px solid color-mix(in srgb, var(--primary) 40%, var(--border));
  border-radius: var(--radius-xl);
  padding: 60px 32px;
  box-shadow: var(--shadow-glow);
}

.cta-box h2 {
  font-size: clamp(2rem, 4vw, 3rem);
  font-weight: 800;
  margin-bottom: 16px;
}

.cta-box p {
  color: var(--text-muted);
  font-size: 1.1rem;
  max-width: 540px;
  margin: 0 auto 32px;
}

/* Footer */
footer {
  border-top: 1px solid var(--border);
  padding: 60px 0 40px;
  background: var(--bg);
  color: var(--text-muted);
  font-size: 0.9rem;
}

.footer-top {
  display: flex;
  align-items: flex-start;
  justify-content: space-between;
  flex-wrap: wrap;
  gap: 32px;
  margin-bottom: 40px;
}

.footer-brand h4 {
  font-size: 1.2rem;
  color: var(--text-main);
  font-weight: 800;
  margin-bottom: 8px;
}

.footer-links {
  display: flex;
  gap: 32px;
  list-style: none;
}

.footer-links a {
  color: var(--text-muted);
  text-decoration: none;
  transition: color 0.2s ease;
}

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

.footer-bottom {
  display: flex;
  align-items: center;
  justify-content: space-between;
  flex-wrap: wrap;
  gap: 16px;
  padding-top: 24px;
  border-top: 1px solid var(--border-subtle);
  font-size: 0.85rem;
}

.footer-bottom a {
  color: var(--primary-light);
  text-decoration: none;
}

/* Responsive */
@media (max-width: 768px) {
  .nav-links {
    display: none;
  }
  .hero {
    padding: 50px 0 40px;
  }
  .footer-top {
    flex-direction: column;
  }
}

/* Demo Video Section */
.demo-section {
  padding: 40px 0 80px;
}

.video-wrapper {
  max-width: 960px;
  margin: 0 auto;
  padding: 12px;
  background: var(--bg-surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-xl);
  box-shadow: var(--shadow-glow), var(--shadow-lg);
  position: relative;
  overflow: hidden;
}

.video-wrapper::before {
  content: "";
  position: absolute;
  top: -50%;
  left: -50%;
  width: 200%;
  height: 200%;
  background: radial-gradient(circle at center, rgba(99, 102, 241, 0.15) 0%, transparent 60%);
  pointer-events: none;
}

.video-container {
  position: relative;
  width: 100%;
  padding-bottom: 56.25%; /* 16:9 aspect ratio */
  height: 0;
  border-radius: var(--radius-lg);
  overflow: hidden;
  background: #000;
}

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