/* ========================================
   Telegram v2 — 深海军蓝+天蓝 极速通讯风
   Navy + Telegram Blue Design System
   ======================================== */

:root {
  --bg: #0a1420;
  --bg2: #0e1c2e;
  --bg3: #13253c;
  --border: #1c3350;
  --border2: #27436b;
  --text: #eaf2fa;
  --text2: #9fb3c8;
  --text3: #5f7891;
  --primary: #2AABEE;
  --primary-deep: #229ED9;
  --green: #43e97b;
  --gradient: linear-gradient(135deg, #2AABEE, #229ED9);
  --grad-glow: rgba(42,171,238,.35);
  --primary-subtle: rgba(42,171,238,.08);
  --radius: 12px;
  --radius-lg: 20px;
  --radius-xl: 28px;
  --radius-full: 9999px;
  --shadow: 0 8px 32px rgba(0,0,0,.4);
  --shadow-lg: 0 16px 56px rgba(0,0,0,.5);
  --max-w: 1280px;
  --transition: .3s cubic-bezier(.4,0,.2,1);
}

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

html {
  scroll-behavior: smooth;
  -webkit-font-smoothing: antialiased;
}

body {
  font-family: 'Inter', 'Noto Sans SC', -apple-system, BlinkMacSystemFont, 'PingFang SC', 'Microsoft YaHei', sans-serif;
  background: var(--bg);
  color: var(--text);
  line-height: 1.7;
  overflow-x: hidden;
  min-height: 100vh;
}

/* ---- 背景效果 ---- */
.bg-effects {
  position: fixed; inset: 0;
  pointer-events: none;
  overflow: hidden;
  z-index: 0;
}
.orb {
  position: absolute;
  border-radius: 50%;
  filter: blur(120px);
  opacity: .12;
  animation: orbFloat 18s ease-in-out infinite;
}
.orb-1 { width: 550px; height: 550px; background: var(--primary); top: -180px; right: -120px; }
.orb-2 { width: 450px; height: 450px; background: #229ED9; bottom: -140px; left: -100px; animation-delay: -8s; }
@keyframes orbFloat {
  0%, 100% { transform: translate(0,0) scale(1); }
  33% { transform: translate(40px,-30px) scale(1.08); }
  66% { transform: translate(-25px,20px) scale(.94); }
}
/* 上浮气泡 */
.bubble {
  position: absolute;
  border-radius: 50%;
  border: 1px solid rgba(42,171,238,.25);
  bottom: -60px;
  opacity: 0;
  animation: bubbleUp 9s linear infinite;
}
.b1 { width: 46px; height: 46px; left: 12%; animation-delay: 0s; }
.b2 { width: 26px; height: 26px; left: 42%; animation-delay: 3s; }
.b3 { width: 60px; height: 60px; left: 78%; animation-delay: 6s; }
@keyframes bubbleUp {
  0% { transform: translateY(0); opacity: 0; }
  15% { opacity: .6; }
  90% { opacity: .3; }
  100% { transform: translateY(-110vh); opacity: 0; }
}
/* 飞机轨迹线 */
.trail-line {
  position: absolute;
  top: 18%; right: 5%;
  width: 320px; height: 2px;
  background: linear-gradient(90deg, transparent, rgba(42,171,238,.5), transparent);
  animation: trailMove 4s linear infinite;
}
@keyframes trailMove {
  0% { transform: translateX(120px); opacity: 0; }
  50% { opacity: 1; }
  100% { transform: translateX(-340px); opacity: 0; }
}

/* ---- 导航 ---- */
.header {
  position: fixed;
  top: 0; left: 0; right: 0;
  z-index: 100;
  height: 68px;
  padding: 0 24px;
  transition: all var(--transition);
}
.header.scrolled {
  background: rgba(14,28,46,.85);
  backdrop-filter: blur(20px);
  -webkit-backdrop-filter: blur(20px);
  border-bottom: 1px solid var(--border);
  box-shadow: 0 4px 24px rgba(0,0,0,.3);
}
.header-inner {
  max-width: var(--max-w);
  margin: 0 auto;
  height: 100%;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 20px;
}
.logo {
  display: flex; align-items: center; gap: 11px;
  text-decoration: none; color: var(--text);
  font-weight: 700; font-size: 20px;
  letter-spacing: -.02em;
}
.logo-icon { width: 36px; height: 36px; flex-shrink: 0; }
.logo-icon svg { display: block; width: 100%; height: 100%; }

.nav-links { display: flex; gap: 8px; }
.nav-links a {
  color: var(--text2);
  text-decoration: none;
  font-size: 14px; font-weight: 500;
  padding: 8px 16px;
  border-radius: var(--radius-full);
  transition: all var(--transition);
}
.nav-links a:hover { color: var(--text); background: rgba(255,255,255,.06); }
.nav-links a.active { color: var(--primary); background: var(--primary-subtle); }

.header-btn {
  display: inline-flex; align-items: center;
  background: var(--gradient);
  color: #fff; text-decoration: none;
  font-size: 13px; font-weight: 600;
  padding: 9px 22px;
  border-radius: var(--radius-full);
  transition: all var(--transition);
  white-space: nowrap;
}
.header-btn:hover { box-shadow: 0 4px 20px var(--grad-glow); transform: translateY(-1px); }

/* 汉堡菜单 */
.menu-btn {
  display: none; flex-direction: column; gap: 5px;
  background: none; border: none; cursor: pointer; padding: 6px;
  z-index: 101;
}
.menu-btn span {
  display: block; width: 24px; height: 2px;
  background: var(--text); border-radius: 2px;
  transition: all var(--transition);
}
.menu-btn.open span:nth-child(1) { transform: translateY(7px) rotate(45deg); }
.menu-btn.open span:nth-child(2) { opacity: 0; }
.menu-btn.open span:nth-child(3) { transform: translateY(-7px) rotate(-45deg); }

@media (max-width: 860px) {
  .nav-links {
    position: fixed; top: 0; right: -100%;
    width: 260px; height: 100vh;
    flex-direction: column;
    background: rgba(14,28,46,.98);
    backdrop-filter: blur(20px);
    padding: 100px 24px 24px;
    gap: 4px;
    transition: right var(--transition);
  }
  .nav-links.open { right: 0; }
  .menu-btn { display: flex; }
  .nav-links a { width: 100%; text-align: center; }
}

/* ---- 按钮系统 ---- */
.btn {
  display: inline-flex; align-items: center; gap: 9px;
  padding: 14px 30px;
  border-radius: var(--radius-full);
  font-size: 15px; font-weight: 600;
  text-decoration: none;
  cursor: pointer;
  transition: all var(--transition);
  border: none;
}
.btn svg { width: 19px; height: 19px; }
.btn-primary {
  background: var(--gradient);
  color: #fff;
  box-shadow: 0 4px 20px var(--grad-glow);
}
.btn-primary:hover { box-shadow: 0 8px 30px var(--grad-glow); transform: translateY(-2px); }
.btn-secondary {
  background: rgba(255,255,255,.06);
  color: var(--text);
  border: 1px solid var(--border2);
}
.btn-secondary:hover { background: rgba(255,255,255,.1); border-color: var(--primary); color: var(--primary); transform: translateY(-2px); }
.btn-lg { padding: 18px 40px; font-size: 17px; }

/* ---- Hero ---- */
.hero {
  position: relative;
  min-height: 100vh;
  display: flex;
  align-items: center;
  padding: 130px 24px 60px;
  z-index: 1;
}
.hero-inner {
  max-width: var(--max-w);
  margin: 0 auto;
  width: 100%;
  display: grid;
  grid-template-columns: 1.1fr 1fr;
  gap: 64px;
  align-items: center;
}
.hero-content { display: flex; flex-direction: column; gap: 24px; }

.badge {
  display: inline-flex; align-items: center; gap: 9px;
  padding: 7px 18px;
  background: var(--primary-subtle);
  border: 1px solid rgba(42,171,238,.3);
  border-radius: var(--radius-full);
  font-size: 13px; font-weight: 500;
  color: var(--primary);
  width: fit-content;
}
.badge-dot {
  width: 8px; height: 8px; border-radius: 50%;
  background: var(--primary);
  animation: dotPulse 2s ease infinite;
}
@keyframes dotPulse {
  0%, 100% { opacity: 1; box-shadow: 0 0 0 0 var(--grad-glow); }
  50% { opacity: .4; box-shadow: 0 0 0 10px transparent; }
}

.hero h1 {
  font-size: clamp(42px, 6vw, 66px);
  font-weight: 900;
  line-height: 1.1;
  letter-spacing: -.03em;
}
.hero h1 em, .section-header em {
  font-style: normal;
  background: var(--gradient);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}
.hero-desc {
  font-size: 17px;
  color: var(--text2);
  line-height: 1.8;
  max-width: 500px;
}
.hero-buttons { display: flex; gap: 16px; flex-wrap: wrap; margin-top: 6px; }
.hero-trust {
  display: flex; gap: 22px;
  font-size: 13px;
  color: var(--text3);
  margin-top: 4px;
}

/* ---- 手机聊天模拟 ---- */
.hero-visual {
  position: relative;
  display: flex;
  justify-content: center;
}
.phone-frame {
  width: 100%; max-width: 320px;
  background: rgba(19,37,60,.9);
  border: 1px solid var(--border2);
  border-radius: 36px;
  padding: 20px 18px 18px;
  box-shadow: var(--shadow-lg), 0 0 80px rgba(42,171,238,.12);
  position: relative;
  animation: phoneFloat 5s ease-in-out infinite;
}
@keyframes phoneFloat {
  0%, 100% { transform: translateY(0); }
  50% { transform: translateY(-10px); }
}
.phone-notch {
  width: 90px; height: 5px;
  background: rgba(255,255,255,.12);
  border-radius: 3px;
  margin: 0 auto 14px;
}
.phone-header {
  display: flex; align-items: center; gap: 12px;
  padding-bottom: 14px;
  border-bottom: 1px solid var(--border);
}
.chat-avatar {
  width: 40px; height: 40px;
  background: var(--gradient);
  border-radius: 50%;
  display: flex; align-items: center; justify-content: center;
  font-size: 17px; font-weight: 800; color: #fff;
  flex-shrink: 0;
}
.chat-info { display: flex; flex-direction: column; }
.chat-name { font-size: 14px; font-weight: 700; }
.chat-status { font-size: 11px; color: var(--green); }

.messages {
  padding: 16px 0;
  display: flex; flex-direction: column; gap: 8px;
  min-height: 180px;
}
.message {
  max-width: 82%;
  padding: 10px 14px;
  border-radius: 16px;
  font-size: 13px;
  line-height: 1.5;
  opacity: 0;
  transform: translateY(8px);
  animation: msgIn .5s ease forwards;
}
@keyframes msgIn { to { opacity: 1; transform: translateY(0); } }
.message.sent {
  align-self: flex-end;
  background: var(--gradient);
  border-bottom-right-radius: 4px;
  animation-delay: .4s;
}
.message.received {
  align-self: flex-start;
  background: rgba(255,255,255,.08);
  border-bottom-left-radius: 4px;
  animation-delay: .2s;
}
.message:nth-child(2) { animation-delay: .9s; }
.message:nth-child(3) { animation-delay: 1.4s; }
.message:nth-child(4) { animation-delay: 1.9s; }

.typing {
  display: none;
  align-self: flex-start;
  gap: 4px;
  padding: 10px 14px;
  background: rgba(255,255,255,.08);
  border-radius: 16px;
  border-bottom-left-radius: 4px;
}
.typing.show { display: flex; }
.typing span {
  width: 6px; height: 6px;
  border-radius: 50%;
  background: var(--text3);
  animation: typingBlink 1.2s infinite;
}
.typing span:nth-child(2) { animation-delay: .2s; }
.typing span:nth-child(3) { animation-delay: .4s; }
@keyframes typingBlink {
  0%, 60%, 100% { opacity: .3; }
  30% { opacity: 1; }
}

.chat-input-bar {
  display: flex; align-items: center; gap: 10px;
}
.chat-input-bar input {
  flex: 1;
  padding: 11px 16px;
  background: rgba(255,255,255,.07);
  border: 1px solid var(--border);
  border-radius: var(--radius-full);
  color: var(--text);
  font-size: 13px;
  outline: none;
}
.chat-input-bar input::placeholder { color: var(--text3); }
.send-icon {
  width: 36px; height: 36px;
  border-radius: 50%;
  background: var(--gradient);
  display: flex; align-items: center; justify-content: center;
  color: #fff;
  flex-shrink: 0;
  cursor: pointer;
}
.send-icon svg { width: 16px; height: 16px; }

/* 浮动卡片 */
.float-card {
  position: absolute;
  display: flex; align-items: center; gap: 11px;
  padding: 13px 16px;
  background: rgba(19,37,60,.92);
  border: 1px solid var(--border2);
  border-radius: var(--radius);
  backdrop-filter: blur(16px);
  -webkit-backdrop-filter: blur(16px);
  box-shadow: var(--shadow);
  z-index: 2;
}
.fc-1 { top: 8%; right: -24px; animation: phoneFloat 4s ease-in-out infinite; }
.fc-2 { bottom: 8%; left: -24px; animation: phoneFloat 4.5s ease-in-out 1s infinite; }
.fc-icon { font-size: 22px; }
.float-card strong { display: block; font-size: 13px; line-height: 1.3; }
.float-card span { font-size: 11px; color: var(--text3); }

/* ---- 数据统计 ---- */
.stats-section {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 20px;
  max-width: 1050px;
  margin: 0 auto;
  padding: 40px 24px 90px;
  position: relative;
  z-index: 1;
}
.stat-card {
  text-align: center;
  padding: 34px 20px;
  background: rgba(19,37,60,.5);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  transition: all var(--transition);
}
.stat-card:hover {
  border-color: rgba(42,171,238,.4);
  transform: translateY(-4px);
  box-shadow: var(--shadow);
}
.stat-number {
  font-size: 40px; font-weight: 800;
  background: var(--gradient);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
  line-height: 1.2;
  margin-bottom: 6px;
}
.stat-number span { font-size: 17px; font-weight: 600; }
.stat-label { font-size: 13px; color: var(--text3); }

/* ---- 通用区块头 ---- */
.section-header { text-align: center; margin-bottom: 56px; }
.section-tag {
  display: inline-block;
  font-size: 12px; font-weight: 600; text-transform: uppercase; letter-spacing: .1em;
  color: var(--primary);
  background: var(--primary-subtle);
  padding: 6px 16px;
  border-radius: var(--radius-full);
  margin-bottom: 18px;
  border: 1px solid rgba(42,171,238,.25);
}
.section-header h2 {
  font-size: clamp(30px, 4.5vw, 44px);
  font-weight: 800;
  letter-spacing: -.02em;
  margin-bottom: 12px;
}
.section-header p { font-size: 16px; color: var(--text2); }

/* ---- 核心功能 ---- */
.features-section {
  max-width: var(--max-w);
  margin: 0 auto;
  padding: 20px 24px 90px;
  position: relative;
  z-index: 1;
}
.features-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 20px;
}
.feature-card {
  position: relative;
  background: rgba(19,37,60,.5);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 32px 28px;
  transition: all var(--transition);
  overflow: hidden;
}
.feature-card::after {
  content: '';
  position: absolute; top: 0; left: 0; right: 0;
  height: 2px;
  background: var(--gradient);
  opacity: 0;
  transition: opacity var(--transition);
}
.feature-card:hover {
  background: rgba(19,37,60,.8);
  border-color: rgba(42,171,238,.35);
  transform: translateY(-4px);
  box-shadow: var(--shadow);
}
.feature-card:hover::after { opacity: 1; }
.feature-icon {
  width: 52px; height: 52px;
  border-radius: var(--radius);
  display: flex; align-items: center; justify-content: center;
  margin-bottom: 20px;
}
.feature-icon svg { width: 26px; height: 26px; }
.fi-1 { background: rgba(42,171,238,.12); color: var(--primary); border: 1px solid rgba(42,171,238,.3); }
.fi-2 { background: rgba(67,233,123,.1); color: var(--green); border: 1px solid rgba(67,233,123,.25); }
.fi-3 { background: rgba(168,85,247,.1); color: #a855f7; border: 1px solid rgba(168,85,247,.25); }
.fi-4 { background: rgba(245,158,11,.1); color: #f59e0b; border: 1px solid rgba(245,158,11,.25); }
.fi-5 { background: rgba(34,211,238,.1); color: #22d3ee; border: 1px solid rgba(34,211,238,.25); }
.fi-6 { background: rgba(236,72,153,.1); color: #ec4899; border: 1px solid rgba(236,72,153,.25); }
.feature-num {
  position: absolute; top: 22px; right: 24px;
  font-size: 30px; font-weight: 900;
  color: rgba(255,255,255,.04);
  line-height: 1;
}
.feature-card h3 { font-size: 17px; font-weight: 700; margin-bottom: 10px; }
.feature-card p { font-size: 14px; color: var(--text2); line-height: 1.7; }

/* ---- 亮点 ---- */
.highlights-section {
  max-width: 1050px;
  margin: 0 auto;
  padding: 0 24px 90px;
  position: relative;
  z-index: 1;
}
.highlights-grid {
  display: grid;
  grid-template-columns: repeat(5, 1fr);
  gap: 16px;
}
.highlight-card {
  text-align: center;
  padding: 28px 14px;
  background: rgba(19,37,60,.5);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  transition: all var(--transition);
  cursor: pointer;
}
.highlight-card:hover {
  transform: translateY(-4px);
  background: rgba(19,37,60,.8);
  border-color: rgba(42,171,238,.35);
  box-shadow: var(--shadow);
}
.highlight-icon { font-size: 32px; margin-bottom: 12px; }
.highlight-card h4 { font-size: 15px; margin-bottom: 6px; }
.highlight-card p { font-size: 12px; color: var(--text3); line-height: 1.5; }

/* ---- CTA ---- */
.cta-section {
  max-width: 860px;
  margin: 0 auto;
  padding: 0 24px 100px;
  position: relative;
  z-index: 1;
}
.cta-card {
  padding: 64px 48px;
  background: linear-gradient(135deg, rgba(42,171,238,.1), rgba(34,158,217,.04));
  border: 1px solid rgba(42,171,238,.3);
  border-radius: var(--radius-xl);
  text-align: center;
  position: relative;
  overflow: hidden;
}
.cta-card::before {
  content: '';
  position: absolute; top: -50%; left: 50%;
  transform: translateX(-50%);
  width: 560px; height: 560px;
  background: radial-gradient(circle, rgba(42,171,238,.18), transparent 70%);
  pointer-events: none;
}
.cta-card h2 { font-size: clamp(26px, 3.5vw, 36px); font-weight: 800; margin-bottom: 12px; position: relative; }
.cta-card p { font-size: 15px; color: var(--text2); margin-bottom: 32px; position: relative; }
.cta-card .btn { position: relative; }

/* ---- 页脚 ---- */
.footer {
  border-top: 1px solid var(--border);
  background: var(--bg2);
  padding: 44px 24px 32px;
  position: relative;
  z-index: 1;
}
.footer-inner {
  max-width: var(--max-w);
  margin: 0 auto;
  display: flex; align-items: center; justify-content: space-between;
  flex-wrap: wrap; gap: 24px;
}
.footer-brand { display: flex; align-items: center; gap: 14px; }
.footer-logo { width: 34px; height: 34px; }
.footer-logo svg { width: 100%; height: 100%; }
.footer-name { font-size: 16px; font-weight: 700; }
.footer-tagline { font-size: 12px; color: var(--text3); }
.footer-links { display: flex; gap: 24px; }
.footer-links a {
  font-size: 13px;
  color: var(--text2);
  text-decoration: none;
  transition: color var(--transition);
}
.footer-links a:hover { color: var(--primary); }
.footer-copy { font-size: 12px; color: var(--text3); width: 100%; text-align: center; padding-top: 18px; border-top: 1px solid var(--border); }

/* ---- 下载页 ---- */
.download-page {
  position: relative;
  min-height: 100vh;
  padding: 140px 24px 100px;
  z-index: 1;
}
.dl-inner { max-width: 1120px; margin: 0 auto; }
.dl-header { text-align: center; margin-bottom: 60px; }
.dl-logo-ring {
  position: relative;
  width: 108px; height: 108px;
  margin: 0 auto 28px;
}
.dl-logo-ring > svg {
  width: 100%; height: 100%;
  animation: ringRotate 8s linear infinite;
}
@keyframes ringRotate { to { transform: rotate(360deg); } }
.dl-logo-core {
  position: absolute; inset: 18px;
  display: flex; align-items: center; justify-content: center;
}
.dl-logo-core svg {
  width: 100%; height: 100%;
  filter: drop-shadow(0 0 24px rgba(42,171,238,.4));
}
.dl-header h1 {
  font-size: clamp(32px, 5vw, 46px);
  font-weight: 800;
  letter-spacing: -.03em;
  margin-bottom: 10px;
}
.dl-header p { font-size: 16px; color: var(--text2); }

.dl-grid {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 20px;
  margin-bottom: 72px;
}
.dl-card {
  position: relative;
  background: rgba(19,37,60,.5);
  border: 1px solid var(--border);
  border-radius: var(--radius-xl);
  padding: 34px 30px;
  text-align: center;
  transition: all var(--transition);
}
.dl-card:hover {
  border-color: rgba(42,171,238,.35);
  background: rgba(19,37,60,.8);
  transform: translateY(-4px);
  box-shadow: var(--shadow-lg);
}
.dl-card.featured {
  background: linear-gradient(180deg, rgba(42,171,238,.08), rgba(34,158,217,.03));
  border-color: rgba(42,171,238,.4);
  box-shadow: 0 0 60px rgba(42,171,238,.1);
}
.dl-tag {
  position: absolute; top: 18px; right: 18px;
  font-size: 11px; font-weight: 700;
  background: var(--gradient);
  color: #fff;
  padding: 4px 14px;
  border-radius: var(--radius-full);
}
.dl-icon {
  width: 62px; height: 62px;
  margin: 0 auto 16px;
  border-radius: var(--radius-lg);
  background: var(--primary-subtle);
  border: 1px solid rgba(42,171,238,.3);
  display: flex; align-items: center; justify-content: center;
  color: var(--primary);
  transition: all var(--transition);
}
.dl-icon svg { width: 30px; height: 30px; }
.dl-card:hover .dl-icon { box-shadow: 0 0 28px rgba(42,171,238,.3); }
.dl-card h3 { font-size: 20px; font-weight: 800; margin-bottom: 4px; }
.dl-ver { font-size: 13px; color: var(--text3); display: block; margin-bottom: 18px; }
.dl-specs {
  text-align: left;
  background: rgba(255,255,255,.02);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 12px 18px;
  margin-bottom: 18px;
}
.dl-spec {
  display: flex; justify-content: space-between;
  font-size: 13px;
  padding: 5px 0;
}
.dl-spec span { color: var(--text3); }
.dl-spec strong { font-weight: 600; color: var(--text2); }
.dl-btn { width: 100%; justify-content: center; }

/* 安装指引 */
.guide-section { margin-bottom: 56px; }
.guide-row {
  display: flex; align-items: stretch; justify-content: center;
  gap: 18px;
}
.guide-step {
  flex: 1; max-width: 300px;
  text-align: center;
  padding: 30px 22px;
  background: rgba(19,37,60,.5);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  transition: all var(--transition);
}
.guide-step:hover {
  border-color: rgba(42,171,238,.35);
  transform: translateY(-4px);
  box-shadow: var(--shadow);
}
.gs-num {
  font-size: 34px; font-weight: 900;
  background: var(--gradient);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
  line-height: 1.1;
  margin-bottom: 10px;
}
.guide-step h4 { font-size: 16px; font-weight: 700; margin-bottom: 8px; }
.guide-step p { font-size: 13px; color: var(--text2); line-height: 1.7; }
.guide-arr {
  display: flex; align-items: center;
  color: var(--text3);
  font-size: 20px;
  flex-shrink: 0;
}
.back-link {
  display: inline-flex; align-items: center; gap: 8px;
  font-size: 14px; color: var(--text2);
  text-decoration: none;
  transition: color var(--transition);
}
.back-link svg { width: 17px; height: 17px; }
.back-link:hover { color: var(--primary); }

/* ---- 404 页 ---- */
.error-page {
  position: relative;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  text-align: center;
  padding: 130px 24px 60px;
  z-index: 1;
}
.error-visual { margin-bottom: 20px; }
.plane-fly { position: relative; padding-right: 60px; }
.plane-icon {
  display: inline-block;
  animation: planeFly 3.5s ease-in-out infinite;
  filter: drop-shadow(0 0 30px rgba(42,171,238,.45));
}
@keyframes planeFly {
  0%, 100% { transform: translate(0,0) rotate(0deg); }
  50% { transform: translate(-18px,-12px) rotate(-8deg); }
}
.trail {
  position: absolute;
  height: 2px;
  border-radius: 2px;
  top: 40%;
  right: 20px;
  transform-origin: right center;
}
.trail-1 {
  width: 110px;
  transform: rotate(14deg);
  background: linear-gradient(90deg, transparent, rgba(42,171,238,.45));
}
.trail-2 {
  width: 78px;
  top: 50%;
  right: 8px;
  transform: rotate(24deg);
  background: linear-gradient(90deg, transparent, rgba(42,171,238,.3));
}
.trail-3 {
  width: 50px;
  top: 58%;
  right: -2px;
  transform: rotate(34deg);
  background: linear-gradient(90deg, transparent, rgba(42,171,238,.18));
}
.error-code {
  font-size: clamp(80px, 13vw, 140px);
  font-weight: 900;
  line-height: 1;
  letter-spacing: -.04em;
  background: var(--gradient);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
  margin-bottom: 12px;
}
.error-code span { animation: blink 2s ease-in-out infinite; }
@keyframes blink { 0%, 100% { opacity: 1; } 50% { opacity: .35; } }
.error-page h1 { font-size: 28px; font-weight: 700; margin-bottom: 12px; }
.error-page p { font-size: 15px; color: var(--text2); line-height: 1.8; margin-bottom: 36px; }
.error-actions { display: flex; gap: 14px; flex-wrap: wrap; justify-content: center; margin-bottom: 28px; }
.error-countdown { font-size: 13px; color: var(--text3); }

/* ---- 滚动动画（默认可见，JS 标记首屏以下内容延迟显示） ---- */
.reveal { opacity: 1; transform: translateY(0); }
.reveal.is-hidden {
  opacity: 0; transform: translateY(30px);
  transition: opacity .7s ease, transform .7s ease;
}
.reveal.visible { opacity: 1; transform: translateY(0); }

/* ---- 滚动条 ---- */
::-webkit-scrollbar { width: 6px; }
::-webkit-scrollbar-track { background: transparent; }
::-webkit-scrollbar-thumb { background: rgba(42,171,238,.25); border-radius: 3px; }
::-webkit-scrollbar-thumb:hover { background: rgba(42,171,238,.4); }

/* ---- 响应式 ---- */
@media (max-width: 1024px) {
  .hero-inner { grid-template-columns: 1fr; gap: 52px; text-align: center; }
  .hero-content { align-items: center; }
  .hero-desc { max-width: 100%; }
  .hero-buttons, .hero-trust { justify-content: center; }
  .features-grid { grid-template-columns: repeat(2, 1fr); }
  .highlights-grid { grid-template-columns: repeat(3, 1fr); }
  .stats-section { grid-template-columns: repeat(2, 1fr); }
  .float-card.fc-1 { right: 0; }
  .float-card.fc-2 { left: 0; }
}
@media (max-width: 860px) {
  .header-btn { display: none; }
}
@media (max-width: 768px) {
  .hero { padding: 110px 20px 48px; }
  .hero h1 { font-size: 40px; }
  .features-section { padding-bottom: 60px; }
  .highlights-section, .stats-section { padding-bottom: 60px; }
  .cta-section { padding-bottom: 60px; }
  .cta-card { padding: 48px 28px; }
  .download-page { padding: 120px 20px 80px; }
  .dl-grid { grid-template-columns: 1fr; max-width: 460px; margin-left: auto; margin-right: auto; }
  .guide-row { flex-direction: column; align-items: center; }
  .guide-arr { transform: rotate(90deg); }
  .guide-step { max-width: 100%; width: 100%; }
  .error-code { font-size: 80px; }
}
@media (max-width: 560px) {
  .features-grid { grid-template-columns: 1fr; max-width: 400px; margin-left: auto; margin-right: auto; }
  .highlights-grid { grid-template-columns: repeat(2, 1fr); }
  .stats-section { grid-template-columns: repeat(2, 1fr); }
  .float-card { display: none; }
  .error-actions { flex-direction: column; width: 100%; max-width: 300px; }
}