/* =========================
   DESIGN SYSTEM
========================= */
:root {
  --bg: #ffffff;
  --surface: #f5f5f7;
  --border: rgba(0,0,0,0.08);
  --text: #1a1a1a;
  --muted: #888;
  --accent: #0071e3;
  --accent2: #0077ed;
  --font-display: 'Noto Serif SC', serif;
  --font-body: 'DM Sans', -apple-system, 'PingFang SC', sans-serif;
}

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

html { scroll-behavior: smooth; }

body {
  background: var(--bg);
  color: var(--text);
  font-family: var(--font-body);
  font-weight: 300;
  -webkit-font-smoothing: antialiased;
  overflow-x: hidden;
}

a { color: inherit; text-decoration: none; }

/* =========================
   NAV
========================= */
nav {
  position: fixed;
  top: 0; left: 0; right: 0;
  z-index: 100;
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 18px 40px;
  transition: all 0.3s ease;
}

nav.scrolled {
  background: rgba(255,255,255,0.9);
  backdrop-filter: blur(16px);
  padding: 13px 40px;
  border-bottom: 1px solid var(--border);
}

.logo {
  font-family: var(--font-display);
  font-size: 15px;
  font-weight: 700;
  color: var(--text);
  letter-spacing: 0.01em;
}

.nav-right {
  display: flex;
  align-items: center;
  gap: 10px;
}

/* =========================
   BUTTONS
========================= */
.btn {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  border-radius: 8px;
  font-family: var(--font-body);
  font-weight: 500;
  cursor: pointer;
  border: 1px solid transparent;
  transition: all 0.2s ease;
  letter-spacing: 0.01em;
  text-decoration: none;
}

.btn.sm {
  padding: 8px 18px;
  font-size: 13px;
}

.btn.primary {
  background: var(--accent);
  color: #fff;
  border-color: var(--accent);
}
.btn.primary:hover {
  background: var(--accent2);
  border-color: var(--accent2);
  box-shadow: 0 4px 16px rgba(200,168,75,0.3);
}

.btn.secondary {
  background: transparent;
  color: var(--text);
  border-color: var(--border);
}
.btn.secondary:hover {
  border-color: rgba(0,0,0,0.2);
  background: var(--surface);
}

/* =========================
   HERO
========================= */
.hero {
  padding: 100px 40px 80px;
  max-width: 1000px;
  margin: 0 auto;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 0;
}

.hero-video-wrap {
  width: 100%;
  aspect-ratio: 16 / 9;
  border-radius: 14px;
  overflow: hidden;
  border: 1px solid var(--border);
  box-shadow: 0 12px 48px rgba(0,0,0,0.08);
  background: #000;
  position: relative;
}

.hero-video-wrap iframe {
  position: absolute;
  inset: 0;
  width: 100%;
  height: 100%;
}

.hero-caption {
  margin-top: 28px;
  text-align: center;
}

.hero-caption h1 {
  font-family: var(--font-display);
  font-size: clamp(16px, 2vw, 22px);
  font-weight: 700;
  letter-spacing: -0.01em;
  color: var(--text);
  margin-bottom: 0;
  white-space: nowrap;
}

.hero-caption h1 em {
  font-style: normal;
  color: var(--accent);
}

.hero-caption p {
  font-size: 13px;
  color: var(--muted);
  line-height: 1.7;
}

/* =========================
   FOOTER
========================= */
footer {
  border-top: 1px solid var(--border);
  padding: 28px 40px;
}

.footer-inner {
  max-width: 1000px;
  margin: auto;
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.footer-logo {
  font-family: var(--font-display);
  font-size: 13px;
  color: var(--muted);
}

.footer-link {
  font-size: 12px;
  color: var(--muted);
  transition: color 0.2s;
}
.footer-link:hover { color: var(--text); }

/* =========================
   AI FAB
========================= */
.ai-fab {
  position: fixed;
  bottom: 32px;
  right: 32px;
  width: 52px;
  height: 52px;
  border-radius: 50%;
  background: var(--text);
  border: none;
  color: #fff;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  z-index: 200;
  transition: all 0.3s ease;
  box-shadow: 0 6px 24px rgba(0,0,0,0.15);
}

.ai-fab:hover {
  background: #333;
  box-shadow: 0 8px 28px rgba(0,113,227,0.2);
  transform: scale(1.05);
}

.ai-fab-ring {
  position: absolute;
  inset: -5px;
  border-radius: 50%;
  border: 1.5px solid #0071e3;
  opacity: 0;
  animation: fabPulse 3s ease-in-out infinite;
}

@keyframes fabPulse {
  0%, 100% { opacity: 0; transform: scale(1); }
  50% { opacity: 0.5; transform: scale(1.1); }
}

.ai-panel {
  position: fixed;
  bottom: 96px;
  right: 32px;
  width: 260px;
  background: #fff;
  border: 1px solid var(--border);
  border-radius: 14px;
  box-shadow: 0 16px 48px rgba(0,0,0,0.12);
  z-index: 200;
  display: none;
  overflow: hidden;
  animation: panelIn 0.2s cubic-bezier(0.16,1,0.3,1);
}

.ai-panel.open { display: block; }

@keyframes panelIn {
  from { opacity: 0; transform: translateY(10px) scale(0.97); }
  to { opacity: 1; transform: translateY(0) scale(1); }
}

.ai-panel-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 14px 16px;
  border-bottom: 1px solid var(--border);
}

.ai-panel-title {
  display: flex;
  align-items: center;
  gap: 8px;
  font-size: 13px;
  font-weight: 500;
  color: var(--text);
}

.ai-dot {
  width: 7px;
  height: 7px;
  border-radius: 50%;
  background: var(--accent);
  animation: dotBlink 2s ease-in-out infinite;
}

@keyframes dotBlink {
  0%, 100% { opacity: 1; }
  50% { opacity: 0.3; }
}

.ai-panel-close {
  background: none;
  border: none;
  color: var(--muted);
  cursor: pointer;
  font-size: 12px;
  padding: 4px;
  transition: color 0.15s;
}
.ai-panel-close:hover { color: var(--text); }

.ai-panel-body {
  padding: 20px 16px;
  font-size: 13px;
  color: var(--muted);
  line-height: 1.7;
}

.ai-email {
  display: inline-block;
  margin-top: 10px;
  font-size: 12px;
  color: var(--accent);
  transition: color 0.2s;
}
.ai-email:hover { color: var(--accent2); }

/* =========================
   MOBILE
========================= */
@media (max-width: 768px) {
  nav { padding: 14px 20px; }
  nav.scrolled { padding: 11px 20px; }

  .hero { padding: 80px 16px 60px; }
  .hero-video-wrap { border-radius: 10px; }
  .hero-caption h1 { font-size: 20px; }

  footer { padding: 22px 20px; }

  .ai-fab { bottom: 20px; right: 20px; }
  .ai-panel { bottom: 82px; right: 20px; width: calc(100vw - 40px); }
}

/* =========================
   LICENSE DROPDOWN
========================= */
.license-container {
  position: relative;
}

.license-menu {
  display: none;
  position: absolute;
  top: calc(100% + 8px);
  right: 0;
  flex-direction: column;
  background: #fff;
  border: 1px solid var(--border);
  padding: 6px;
  border-radius: 10px;
  box-shadow: 0 8px 32px rgba(0,0,0,0.1);
  min-width: 160px;
  z-index: 50;
  animation: menuIn 0.18s cubic-bezier(0.16,1,0.3,1);
}

.license-menu.open { display: flex; }

.license-menu-item {
  display: block;
  padding: 9px 14px;
  font-size: 13px;
  color: var(--text);
  border-radius: 6px;
  transition: background 0.15s;
  white-space: nowrap;
}
.license-menu-item:hover { background: var(--surface); }

/* =========================
   功能截图区块 (中文)
========================= */
.features-zh {
  width: 100%;
  margin-bottom: 48px;
}

.fz-title {
  font-size: 12px;
  font-weight: 500;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--muted);
  margin-bottom: 36px;
  text-align: left;
}

.fz-block {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 16px;
  margin-bottom: 48px;
  align-items: center;
}

.fz-block.fz-reverse {
  direction: rtl;
}
.fz-block.fz-reverse > * {
  direction: ltr;
}

.fz-info {
  display: flex;
  flex-direction: column;
  justify-content: center;
  padding: 0 8px;
}

.fz-tag {
  font-size: 11px;
  font-weight: 500;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--accent);
  margin-bottom: 10px;
}

.fz-h2 {
  font-family: var(--font-display);
  font-size: 20px;
  font-weight: 700;
  letter-spacing: -0.01em;
  line-height: 1.35;
  margin-bottom: 12px;
  color: var(--text);
}

.fz-p {
  font-size: 13px;
  color: var(--muted);
  line-height: 1.75;
}

.fz-imgs {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 8px;
}

.fz-imgs img {
  width: 100%;
  border-radius: 10px;
  border: 1px solid var(--border);
  display: block;
}

.fz-label {
  font-size: 10px;
  color: var(--muted);
  text-align: center;
  margin-top: 4px;
  letter-spacing: 0.05em;
  text-transform: uppercase;
}

@media (max-width: 768px) {
  .fz-block {
    grid-template-columns: 1fr;
  }
  .fz-block.fz-reverse {
    direction: ltr;
  }
}