:root {
  --bg: #0d1117;
  --bg-card: #161b22;
  --bg-demo: #f8f4ee;
  --fg: #e6e0d4;
  --fg-muted: #8b8477;
  --accent: #c9893a;
  --accent-light: #f5c56c;
  --border: #2d333b;
  --chat-bg: #0d1117;
  --chat-ai-bg: #161b22;
  --chat-user-bg: #1c2d1f;
  --msg-ai: #c9893a;
  --msg-user: #6b9e7a;
  --demo-bg: #f8f4ee;
  --demo-fg: #1a1a1a;
  --light-section-bg: #0d1117;
  --light-section-fg: #e6e0d4;
  --feature-muted: #8b8477;
  --pioneer-bg: #c9893a;
  --closing-bg: #f8f4ee;
  --closing-fg: #1a1a1a;
}

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

html { font-size: 16px; }

body {
  background: var(--bg);
  color: var(--fg);
  font-family: 'DM Sans', system-ui, sans-serif;
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
}

h1, h2, h3, h4 {
  font-family: 'Libre Baskerville', Georgia, serif;
  line-height: 1.2;
}

/* NAV */
.nav-bar {
  padding: 1.5rem 3rem;
  display: flex;
  align-items: center;
  border-bottom: 1px solid var(--border);
  background: var(--bg);
  position: sticky;
  top: 0;
  z-index: 10;
}
.nav-logo {
  font-family: 'Libre Baskerville', serif;
  font-size: 1.35rem;
  font-weight: 700;
  letter-spacing: -0.01em;
  color: var(--fg);
}

/* HERO */
.hero {
  min-height: 90vh;
  display: flex;
  align-items: center;
  padding: 5rem 3rem 4rem;
  background: var(--bg);
  border-bottom: 1px solid var(--border);
}
.hero-inner {
  max-width: 1200px;
  margin: 0 auto;
  width: 100%;
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 5rem;
  align-items: center;
}
.hero-headline {
  font-size: clamp(2.4rem, 4.5vw, 3.8rem);
  font-weight: 700;
  color: var(--fg);
  margin-bottom: 1.5rem;
  letter-spacing: -0.02em;
}
.hero-sub {
  font-size: 1.125rem;
  color: var(--fg-muted);
  line-height: 1.7;
  margin-bottom: 2.5rem;
  max-width: 480px;
}
.hero-stats {
  display: flex;
  align-items: center;
  gap: 1.5rem;
}
.hero-cta {
  display: inline-block;
  background: #c9893a;
  color: #fff;
  padding: 0.75rem 1.75rem;
  border-radius: 10px;
  font-size: 0.95rem;
  font-weight: 600;
  text-decoration: none;
  transition: background 0.2s, transform 0.1s;
  margin-top: 0.5rem;
}
.hero-cta:hover { background: #b07830; }
.hero-cta:active { transform: scale(0.97); }
.stat-num {
  font-family: 'Libre Baskerville', serif;
  font-size: 1.75rem;
  font-weight: 700;
  color: var(--accent);
  display: block;
}
.stat-label {
  font-size: 0.8rem;
  color: var(--fg-muted);
  text-transform: uppercase;
  letter-spacing: 0.08em;
}
.stat-sep {
  width: 1px;
  height: 40px;
  background: var(--border);
}

/* CHAT WIDGET */
.hero-visual {
  display: flex;
  justify-content: center;
}
.chat-widget {
  background: var(--chat-bg);
  border: 1px solid var(--border);
  border-radius: 16px;
  width: 100%;
  max-width: 420px;
  overflow: hidden;
  box-shadow: 0 24px 80px rgba(0,0,0,0.5), 0 0 0 1px rgba(201,137,58,0.15);
}
.chat-header {
  background: var(--bg-card);
  padding: 1rem 1.25rem;
  display: flex;
  justify-content: space-between;
  align-items: center;
  border-bottom: 1px solid var(--border);
}
.chat-scenario-tag {
  font-size: 0.75rem;
  color: var(--accent);
  font-weight: 500;
  letter-spacing: 0.05em;
}
.chat-level {
  font-size: 0.7rem;
  color: var(--fg-muted);
  background: var(--bg);
  padding: 0.2rem 0.6rem;
  border-radius: 20px;
}
.chat-messages {
  padding: 1.25rem;
  display: flex;
  flex-direction: column;
  gap: 1rem;
}
.msg { display: flex; gap: 0.75rem; }
.msg-ai { flex-direction: row; }
.msg-user { flex-direction: row-reverse; }
.msg-avatar {
  width: 32px;
  height: 32px;
  border-radius: 50%;
  background: var(--accent);
  color: #fff;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 0.85rem;
  font-weight: 600;
  flex-shrink: 0;
}
.msg-user .msg-avatar { background: var(--msg-user); color: #fff; }
.msg-content p { margin: 0; }
.msg-ai .msg-content { background: var(--chat-ai-bg); padding: 0.75rem 1rem; border-radius: 0 12px 12px 12px; border: 1px solid var(--border); }
.msg-user .msg-content { background: var(--chat-user-bg); padding: 0.75rem 1rem; border-radius: 12px 0 12px 12px; border: 1px solid rgba(107,158,122,0.3); }
.chinese { font-size: 1rem; color: var(--fg); font-weight: 500; margin-bottom: 0.2rem; }
.pinyin { font-size: 0.78rem; color: var(--fg-muted); font-style: italic; margin-bottom: 0.2rem; }
.english { font-size: 0.78rem; color: var(--accent-light); }
.feedback-tag {
  font-size: 0.72rem;
  color: #6b9e7a;
  margin-top: 0.4rem;
  padding: 0.25rem 0.6rem;
  background: rgba(107,158,122,0.1);
  border-radius: 20px;
  display: inline-block;
}
.chat-input-bar {
  padding: 0.75rem 1rem;
  background: var(--bg-card);
  border-top: 1px solid var(--border);
  display: flex;
  align-items: center;
  justify-content: space-between;
}
.input-hint { font-size: 0.8rem; color: var(--fg-muted); }
.mic-btn { font-size: 1.2rem; cursor: pointer; }

/* DEMO SECTION */
.demo-section {
  background: var(--demo-bg);
  padding: 5rem 3rem;
}
.demo-inner { max-width: 1100px; margin: 0 auto; }
.demo-label {
  text-align: center;
  font-size: 0.85rem;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  color: #7a7267;
  margin-bottom: 3rem;
}
.demo-flow {
  display: flex;
  align-items: flex-start;
  gap: 0;
  justify-content: center;
}
.flow-step {
  flex: 1;
  max-width: 220px;
  text-align: center;
  padding: 0 1rem;
}
.flow-icon { font-size: 2.5rem; margin-bottom: 1rem; }
.flow-title {
  font-family: 'Libre Baskerville', serif;
  font-size: 1rem;
  color: var(--demo-fg);
  margin-bottom: 0.5rem;
}
.flow-desc { font-size: 0.875rem; color: #7a7267; line-height: 1.5; }
.flow-arrow {
  font-size: 1.5rem;
  color: #c9893a;
  align-self: center;
  margin-top: -1rem;
}

/* SCENARIOS */
.scenarios { padding: 6rem 3rem; background: var(--bg); }
.scenarios-inner { max-width: 1100px; margin: 0 auto; }
.section-title {
  font-size: clamp(1.8rem, 3vw, 2.6rem);
  color: var(--fg);
  margin-bottom: 1rem;
  letter-spacing: -0.02em;
}
.section-sub { font-size: 1.05rem; color: var(--fg-muted); margin-bottom: 4rem; max-width: 520px; }
.scenario-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 1.5rem;
}
.scenario-card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: 14px;
  padding: 2rem 1.75rem;
  transition: border-color 0.2s;
}
.scenario-card:hover { border-color: var(--accent); }
.scenario-emoji { font-size: 2rem; margin-bottom: 1rem; }
.scenario-card h3 {
  font-family: 'Libre Baskerville', serif;
  font-size: 1.1rem;
  color: var(--fg);
  margin-bottom: 0.75rem;
}
.scenario-phrase { font-size: 0.95rem; color: var(--accent); margin-bottom: 0.4rem; }
.scenario-eng { font-size: 0.82rem; color: var(--fg-muted); }

/* FEATURES */
.features {
  background: var(--light-section-bg);
  padding: 6rem 3rem;
  border-top: 1px solid var(--border);
  border-bottom: 1px solid var(--border);
}
.features-inner { max-width: 800px; margin: 0 auto; }
.section-title.light { margin-bottom: 3rem; }
.feature-list { display: flex; flex-direction: column; gap: 2.5rem; }
.feature-item {
  display: grid;
  grid-template-columns: 48px 1fr;
  gap: 2rem;
  align-items: start;
}
.feature-icon {
  width: 48px;
  height: 48px;
  background: rgba(201,137,58,0.1);
  border: 1px solid rgba(201,137,58,0.25);
  border-radius: 10px;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.1rem;
  color: var(--accent);
  flex-shrink: 0;
  margin-top: 0.2rem;
}
.feature-body h3 {
  font-size: 1.15rem;
  color: var(--fg);
  margin-bottom: 0.5rem;
}
.feature-body p { font-size: 0.95rem; color: var(--feature-muted); line-height: 1.65; }

/* PIONEER */
.pioneer { background: var(--pioneer-bg); padding: 7rem 3rem; }
.pioneer-inner { max-width: 800px; margin: 0 auto; text-align: center; }
.pioneer-badge {
  display: inline-block;
  font-size: 0.75rem;
  text-transform: uppercase;
  letter-spacing: 0.12em;
  color: #4a2800;
  background: rgba(0,0,0,0.12);
  padding: 0.35rem 1rem;
  border-radius: 20px;
  margin-bottom: 2rem;
}
.pioneer-headline {
  font-size: clamp(2rem, 3.5vw, 3rem);
  color: #1a0c00;
  margin-bottom: 1.5rem;
  letter-spacing: -0.02em;
}
.pioneer-sub { font-size: 1.05rem; color: #4a2800; line-height: 1.7; margin-bottom: 2.5rem; max-width: 560px; margin-left: auto; margin-right: auto; }
.pioneer-philosophy {
  border-top: 1px solid rgba(0,0,0,0.15);
  padding-top: 2rem;
  margin-top: 1rem;
}
.philosophy-text {
  font-family: 'Libre Baskerville', serif;
  font-style: italic;
  font-size: 1rem;
  color: #4a2800;
  line-height: 1.65;
  max-width: 580px;
  margin: 0 auto;
}

/* CLOSING */
.closing {
  background: var(--closing-bg);
  padding: 7rem 3rem;
}
.closing-inner { max-width: 900px; margin: 0 auto; text-align: center; }
.closing-headline {
  font-size: clamp(1.8rem, 3vw, 2.8rem);
  color: var(--closing-fg);
  margin-bottom: 1.5rem;
  letter-spacing: -0.02em;
  line-height: 1.3;
}
.closing-sub { font-size: 1.05rem; color: #5a5248; line-height: 1.7; margin-bottom: 1.5rem; max-width: 600px; margin-left: auto; margin-right: auto; }
.closing-fine {
  font-size: 0.875rem;
  color: #8b8477;
  text-transform: uppercase;
  letter-spacing: 0.08em;
}

/* FOOTER */
.footer { background: var(--bg); padding: 3rem; border-top: 1px solid var(--border); }
.footer-inner { max-width: 1100px; margin: 0 auto; text-align: center; }
.footer-logo { font-family: 'Libre Baskerville', serif; font-size: 1.3rem; color: var(--fg); margin-bottom: 0.5rem; }
.footer-tagline { font-size: 0.85rem; color: var(--fg-muted); margin-bottom: 0.5rem; }
.footer-copy { font-size: 0.78rem; color: var(--fg-muted); }

/* RESPONSIVE */
@media (max-width: 900px) {
  .hero-inner { grid-template-columns: 1fr; gap: 3rem; }
  .hero-visual { order: -1; }
  .scenario-grid { grid-template-columns: repeat(2, 1fr); }
  .demo-flow { flex-direction: column; gap: 2rem; align-items: center; }
  .flow-step { max-width: 320px; }
  .flow-arrow { transform: rotate(90deg); }
}
@media (max-width: 600px) {
  .hero { padding: 3rem 1.5rem; }
  .scenarios { padding: 4rem 1.5rem; }
  .scenario-grid { grid-template-columns: 1fr; }
  .demo-section { padding: 4rem 1.5rem; }
  .features { padding: 4rem 1.5rem; }
  .pioneer { padding: 4rem 1.5rem; }
  .closing { padding: 4rem 1.5rem; }
  .nav-bar { padding: 1rem 1.5rem; }
}