/* 纸飞机 Telegram 中文版官网 — 电脑端专用样式 */
:root {
  --tg-blue: #2aabee;
  --tg-blue-dark: #229ed9;
  --tg-blue-deep: #1e8bc3;
  --tg-blue-light: #e8f6fc;
  --tg-gradient: linear-gradient(135deg, #2aabee 0%, #229ed9 50%, #1e8bc3 100%);
  --tg-gradient-soft: linear-gradient(180deg, #e8f6fc 0%, #ffffff 100%);
  --text: #1a1a2e;
  --text-secondary: #4a5568;
  --text-muted: #718096;
  --bg: #ffffff;
  --bg-alt: #f7fafc;
  --border: #e2e8f0;
  --shadow: 0 8px 32px rgba(42, 171, 238, 0.12);
  --shadow-lg: 0 20px 60px rgba(42, 171, 238, 0.18);
  --radius: 12px;
  --radius-lg: 20px;
  --header-h: 72px;
  --container: 1200px;
}

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

html {
  scroll-behavior: smooth;
  font-size: 16px;
}

body {
  font-family: "Segoe UI", "Microsoft YaHei", "PingFang SC", "Helvetica Neue", Arial, sans-serif;
  color: var(--text);
  background: var(--bg);
  line-height: 1.65;
  min-width: 1024px;
  -webkit-font-smoothing: antialiased;
}

a { color: var(--tg-blue); text-decoration: none; transition: color 0.2s; }
a:hover { color: var(--tg-blue-deep); }

img { max-width: 100%; display: block; }
ul { list-style: none; }

.container {
  max-width: var(--container);
  margin: 0 auto;
  padding: 0 32px;
}

/* Header */
.header {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  height: var(--header-h);
  background: rgba(255, 255, 255, 0.96);
  backdrop-filter: blur(16px);
  border-bottom: 1px solid var(--border);
  z-index: 1000;
}

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

.logo {
  display: flex;
  align-items: center;
  gap: 12px;
  font-size: 22px;
  font-weight: 700;
  color: var(--text);
}

.logo-icon {
  width: 44px;
  height: 44px;
  background: var(--tg-gradient);
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  color: #fff;
  font-size: 22px;
  box-shadow: 0 4px 16px rgba(42, 171, 238, 0.35);
}

.nav {
  display: flex;
  align-items: center;
  gap: 4px;
}

.nav a {
  padding: 10px 18px;
  border-radius: 10px;
  color: var(--text-secondary);
  font-size: 15px;
  font-weight: 500;
}

.nav a:hover,
.nav a.active {
  color: var(--tg-blue);
  background: var(--tg-blue-light);
}

.header-download {
  padding: 12px 28px;
  background: var(--tg-gradient);
  color: #fff;
  border: none;
  border-radius: 12px;
  font-size: 15px;
  font-weight: 600;
  cursor: pointer;
  box-shadow: 0 4px 16px rgba(42, 171, 238, 0.3);
  transition: transform 0.2s, box-shadow 0.2s;
}

.header-download:hover {
  transform: translateY(-2px);
  box-shadow: 0 8px 24px rgba(42, 171, 238, 0.4);
}

/* Buttons */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  padding: 14px 32px;
  border-radius: 12px;
  font-size: 16px;
  font-weight: 600;
  border: none;
  cursor: pointer;
  transition: all 0.25s;
}

.btn-primary {
  background: var(--tg-gradient);
  color: #fff;
  box-shadow: 0 6px 20px rgba(42, 171, 238, 0.35);
}

.btn-primary:hover {
  transform: translateY(-2px);
  box-shadow: 0 10px 28px rgba(42, 171, 238, 0.45);
}

.btn-outline {
  background: transparent;
  color: var(--tg-blue);
  border: 2px solid var(--tg-blue);
}

.btn-outline:hover {
  background: var(--tg-blue-light);
}

.btn-lg { padding: 18px 40px; font-size: 17px; }

/* Hero */
.hero {
  padding: calc(var(--header-h) + 80px) 0 100px;
  background: var(--tg-gradient-soft);
  position: relative;
  overflow: hidden;
}

.hero::before {
  content: "";
  position: absolute;
  top: -200px;
  right: -100px;
  width: 600px;
  height: 600px;
  background: radial-gradient(circle, rgba(42, 171, 238, 0.15) 0%, transparent 70%);
  border-radius: 50%;
}

.hero-inner {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 80px;
  align-items: center;
  position: relative;
}

.hero-badge {
  display: inline-block;
  padding: 6px 16px;
  background: var(--tg-blue-light);
  color: var(--tg-blue-deep);
  border-radius: 20px;
  font-size: 13px;
  font-weight: 600;
  margin-bottom: 20px;
}

.hero h1 {
  font-size: 52px;
  font-weight: 800;
  line-height: 1.15;
  margin-bottom: 24px;
  letter-spacing: -0.02em;
}

.hero h1 span {
  background: var(--tg-gradient);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.hero-desc {
  font-size: 18px;
  color: var(--text-secondary);
  margin-bottom: 36px;
  max-width: 520px;
}

.hero-actions {
  display: flex;
  gap: 16px;
}

/* Chat mockup */
.chat-mockup {
  background: #fff;
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-lg);
  overflow: hidden;
  border: 1px solid var(--border);
}

.mockup-header {
  background: var(--tg-gradient);
  padding: 16px 20px;
  color: #fff;
  display: flex;
  align-items: center;
  gap: 12px;
}

.mockup-avatar {
  width: 40px;
  height: 40px;
  background: rgba(255,255,255,0.25);
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 18px;
}

.mockup-body {
  padding: 24px;
  min-height: 320px;
  background: linear-gradient(180deg, #e8f6fc 0%, #fff 100%);
}

.chat-bubble {
  max-width: 75%;
  padding: 12px 16px;
  border-radius: 16px;
  margin-bottom: 12px;
  font-size: 14px;
  line-height: 1.5;
}

.chat-bubble.in {
  background: #fff;
  border: 1px solid var(--border);
  border-bottom-left-radius: 4px;
}

.chat-bubble.out {
  background: var(--tg-blue);
  color: #fff;
  margin-left: auto;
  border-bottom-right-radius: 4px;
}

/* Stats */
.stats {
  padding: 60px 0;
  background: var(--bg);
  border-top: 1px solid var(--border);
  border-bottom: 1px solid var(--border);
}

.stats-grid {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 40px;
  text-align: center;
}

.stat-num {
  font-size: 42px;
  font-weight: 800;
  color: var(--tg-blue);
  line-height: 1.2;
}

.stat-label {
  color: var(--text-muted);
  font-size: 15px;
  margin-top: 8px;
}

/* Sections */
.section {
  padding: 90px 0;
}

.section-alt {
  background: var(--bg-alt);
}

.section-head {
  text-align: center;
  max-width: 680px;
  margin: 0 auto 60px;
}

.section-head h2 {
  font-size: 38px;
  font-weight: 700;
  margin-bottom: 16px;
}

.section-head p {
  font-size: 17px;
  color: var(--text-secondary);
}

/* Feature cards */
.features-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 28px;
}

.feature-card {
  background: var(--bg);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 36px 28px;
  transition: all 0.3s;
}

.feature-card:hover {
  transform: translateY(-6px);
  box-shadow: var(--shadow-lg);
  border-color: var(--tg-blue);
}

.feature-icon {
  width: 56px;
  height: 56px;
  background: var(--tg-blue-light);
  border-radius: 14px;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 26px;
  margin-bottom: 20px;
}

.feature-card h3 {
  font-size: 20px;
  margin-bottom: 12px;
}

.feature-card p {
  color: var(--text-secondary);
  font-size: 15px;
}

/* Page hero */
.page-hero {
  padding: calc(var(--header-h) + 48px) 0 56px;
  background: var(--tg-gradient-soft);
  text-align: center;
}

.page-hero h1 {
  font-size: 42px;
  font-weight: 800;
  margin-bottom: 16px;
}

.page-hero p {
  font-size: 18px;
  color: var(--text-secondary);
  max-width: 640px;
  margin: 0 auto;
}

.breadcrumb {
  display: flex;
  justify-content: center;
  gap: 8px;
  margin-bottom: 24px;
  font-size: 14px;
  color: var(--text-muted);
}

.breadcrumb a { color: var(--text-muted); }
.breadcrumb a:hover { color: var(--tg-blue); }

/* Download cards */
.download-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 28px;
}

.download-card {
  background: var(--bg);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 40px 32px;
  text-align: center;
  transition: all 0.3s;
}

.download-card:hover {
  border-color: var(--tg-blue);
  box-shadow: var(--shadow);
}

.download-icon { font-size: 48px; margin-bottom: 16px; }
.download-card h3 { font-size: 20px; margin-bottom: 8px; }
.download-card p { color: var(--text-muted); font-size: 14px; margin-bottom: 24px; }

/* FAQ */
.faq-list { max-width: 820px; margin: 0 auto; }

.faq-item {
  border: 1px solid var(--border);
  border-radius: var(--radius);
  margin-bottom: 12px;
  overflow: hidden;
}

.faq-question {
  width: 100%;
  padding: 20px 24px;
  background: var(--bg);
  border: none;
  text-align: left;
  font-size: 16px;
  font-weight: 600;
  cursor: pointer;
  display: flex;
  justify-content: space-between;
  align-items: center;
  color: var(--text);
}

.faq-question:hover { background: var(--bg-alt); }

.faq-answer {
  padding: 0 24px;
  max-height: 0;
  overflow: hidden;
  transition: all 0.3s;
  color: var(--text-secondary);
  font-size: 15px;
}

.faq-item.open .faq-answer {
  padding: 0 24px 20px;
  max-height: 400px;
}

.faq-toggle { color: var(--tg-blue); font-size: 20px; transition: transform 0.3s; }
.faq-item.open .faq-toggle { transform: rotate(45deg); }

/* Security blocks */
.security-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 48px;
  align-items: center;
}

.security-list li {
  display: flex;
  gap: 16px;
  margin-bottom: 24px;
}

.security-list .icon {
  width: 48px;
  height: 48px;
  background: var(--tg-blue-light);
  border-radius: 12px;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 22px;
  flex-shrink: 0;
}

/* Timeline */
.timeline-item {
  display: flex;
  gap: 28px;
  margin-bottom: 36px;
}

.timeline-year {
  width: 80px;
  font-weight: 800;
  color: var(--tg-blue);
  font-size: 18px;
  flex-shrink: 0;
}

/* CTA */
.cta {
  padding: 90px 0;
  background: var(--tg-gradient);
  text-align: center;
  color: #fff;
}

.cta h2 { font-size: 36px; margin-bottom: 16px; }
.cta p { font-size: 18px; opacity: 0.92; margin-bottom: 32px; }
.cta .btn-primary { background: #fff; color: var(--tg-blue); }
.cta .btn-primary:hover { background: var(--tg-blue-light); }

/* Footer */
.footer {
  background: #0f172a;
  color: #94a3b8;
  padding: 64px 0 32px;
}

.footer-grid {
  display: grid;
  grid-template-columns: 2fr 1fr 1fr 1fr;
  gap: 48px;
  margin-bottom: 48px;
}

.footer-brand p { margin-top: 16px; font-size: 14px; line-height: 1.7; }
.footer-col h4 { color: #fff; font-size: 15px; margin-bottom: 18px; }
.footer-col li { margin-bottom: 10px; }
.footer-col a { color: #94a3b8; font-size: 14px; }
.footer-col a:hover { color: #fff; }

.footer-bottom {
  border-top: 1px solid #1e293b;
  padding-top: 24px;
  display: flex;
  justify-content: space-between;
  font-size: 13px;
}

.footer-bottom a { color: #64748b; }
.footer-bottom a:hover { color: #fff; }

/* Content */
.content-page { max-width: 820px; margin: 0 auto; }
.content-page h2 { font-size: 26px; margin: 40px 0 16px; }
.content-page p, .content-page li { color: var(--text-secondary); margin-bottom: 12px; font-size: 15px; }
.content-page ul { padding-left: 24px; list-style: disc; }