/* ===== 第1套：清爽官方风 - 安全下载中心 ===== */
/* 白底 + Chrome蓝色系，简洁大方 */

:root {
  --primary: #1a73e8;
  --primary-dark: #1557b0;
  --primary-light: #e8f0fe;
  --accent: #34a853;
  --text: #202124;
  --text-secondary: #5f6368;
  --text-muted: #80868b;
  --bg: #ffffff;
  --bg-secondary: #f8f9fa;
  --bg-card: #ffffff;
  --border: #dadce0;
  --border-light: #e8eaed;
  --shadow: 0 1px 2px 0 rgba(60,64,67,0.08), 0 1px 3px 1px rgba(60,64,67,0.06);
  --shadow-hover: 0 4px 12px rgba(60,64,67,0.15);
  --radius: 8px;
  --radius-lg: 12px;
  --max-width: 1200px;
  --nav-height: 64px;
}

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

html { scroll-behavior: smooth; }

body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  color: var(--text);
  background: var(--bg);
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
}

/* ===== Header & Nav ===== */
header {
  position: fixed;
  top: 0; left: 0; right: 0;
  height: var(--nav-height);
  background: var(--bg);
  border-bottom: 1px solid var(--border-light);
  z-index: 1000;
  box-shadow: var(--shadow);
}

nav {
  max-width: var(--max-width);
  margin: 0 auto;
  height: 100%;
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0 24px;
}

.nav-brand {
  display: flex;
  align-items: center;
  gap: 10px;
  font-size: 20px;
  font-weight: 600;
  color: var(--text);
  text-decoration: none;
}

.nav-brand svg { width: 32px; height: 32px; }

.nav-links {
  display: flex;
  list-style: none;
  gap: 4px;
}

.nav-links a {
  display: block;
  padding: 8px 18px;
  border-radius: 20px;
  color: var(--text-secondary);
  text-decoration: none;
  font-size: 15px;
  font-weight: 500;
  transition: all 0.2s ease;
}

.nav-links a:hover {
  color: var(--primary);
  background: var(--primary-light);
}

.nav-links a.active {
  color: var(--primary);
  background: var(--primary-light);
}

/* ===== Main Content ===== */
main { padding-top: var(--nav-height); }

.container {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 24px;
}

/* ===== Hero Section ===== */
.hero {
  background: linear-gradient(180deg, #e8f0fe 0%, var(--bg) 100%);
  padding: 80px 0 60px;
  text-align: center;
}

.hero h1 {
  font-size: 48px;
  font-weight: 700;
  color: var(--text);
  margin-bottom: 16px;
  line-height: 1.2;
}

.hero h1 span { color: var(--primary); }

.hero-subtitle {
  font-size: 20px;
  color: var(--text-secondary);
  max-width: 640px;
  margin: 0 auto 36px;
}

.hero-actions {
  display: flex;
  gap: 16px;
  justify-content: center;
  margin-bottom: 24px;
}

/* ===== Buttons ===== */
.btn {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 14px 32px;
  border-radius: var(--radius);
  font-size: 16px;
  font-weight: 600;
  cursor: pointer;
  border: none;
  text-decoration: none;
  transition: all 0.2s ease;
}

.btn-primary {
  background: var(--primary);
  color: #fff;
}

.btn-primary:hover {
  background: var(--primary-dark);
  transform: translateY(-1px);
  box-shadow: var(--shadow-hover);
}

.btn-secondary {
  background: #fff;
  color: var(--primary);
  border: 1px solid var(--border);
}

.btn-secondary:hover {
  background: var(--primary-light);
  border-color: var(--primary);
}

.btn-lg { padding: 16px 40px; font-size: 18px; border-radius: var(--radius-lg); }

.btn-sm { padding: 10px 20px; font-size: 14px; }

/* ===== Section Styles ===== */
.section {
  padding: 64px 0;
}

.section-title {
  font-size: 32px;
  font-weight: 700;
  text-align: center;
  margin-bottom: 12px;
  color: var(--text);
}

.section-subtitle {
  font-size: 17px;
  color: var(--text-secondary);
  text-align: center;
  max-width: 600px;
  margin: 0 auto 48px;
}

/* ===== Feature Cards ===== */
.feature-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(340px, 1fr));
  gap: 24px;
}

.feature-card {
  background: var(--bg-card);
  border: 1px solid var(--border-light);
  border-radius: var(--radius-lg);
  padding: 32px;
  transition: all 0.25s ease;
}

.feature-card:hover {
  box-shadow: var(--shadow-hover);
  transform: translateY(-2px);
  border-color: var(--border);
}

.feature-card .icon-wrap {
  width: 48px;
  height: 48px;
  border-radius: var(--radius);
  background: var(--primary-light);
  display: flex;
  align-items: center;
  justify-content: center;
  margin-bottom: 16px;
}

.feature-card .icon-wrap svg { width: 24px; height: 24px; color: var(--primary); }

.feature-card h3 {
  font-size: 18px;
  font-weight: 600;
  margin-bottom: 8px;
  color: var(--text);
}

.feature-card p {
  font-size: 15px;
  color: var(--text-secondary);
  line-height: 1.7;
}

/* ===== Download Cards ===== */
.download-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
  gap: 20px;
}

.download-card {
  background: var(--bg-card);
  border: 1px solid var(--border-light);
  border-radius: var(--radius-lg);
  padding: 28px;
  text-align: center;
  transition: all 0.25s ease;
}

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

.download-card svg { width: 40px; height: 40px; margin-bottom: 12px; color: var(--primary); }

.download-card h4 { font-size: 17px; font-weight: 600; margin-bottom: 4px; }

.download-card .version { font-size: 13px; color: var(--text-muted); margin-bottom: 16px; }

/* ===== Stats Bar ===== */
.stats-bar {
  background: var(--bg-secondary);
  border-top: 1px solid var(--border-light);
  border-bottom: 1px solid var(--border-light);
  padding: 40px 0;
}

.stats-grid {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 32px;
  text-align: center;
}

.stat-item .stat-num {
  font-size: 36px;
  font-weight: 700;
  color: var(--primary);
}

.stat-item .stat-label {
  font-size: 14px;
  color: var(--text-secondary);
  margin-top: 4px;
}

/* ===== Scrolling Bar ===== */
.scroll-bar {
  background: var(--primary);
  color: #fff;
  padding: 14px 0;
  overflow: hidden;
  white-space: nowrap;
}

.scroll-content {
  display: inline-block;
  animation: scroll 30s linear infinite;
  font-size: 14px;
  opacity: 0.9;
}

@keyframes scroll {
  0% { transform: translateX(0); }
  100% { transform: translateX(-50%); }
}

/* ===== FAQ ===== */
.faq-item {
  border-bottom: 1px solid var(--border-light);
  padding: 24px 0;
}

.faq-item h3 {
  font-size: 17px;
  font-weight: 600;
  color: var(--text);
  margin-bottom: 10px;
  display: flex;
  align-items: center;
  gap: 10px;
}

.faq-item h3 svg { width: 20px; height: 20px; color: var(--primary); flex-shrink: 0; }

.faq-item p {
  font-size: 15px;
  color: var(--text-secondary);
  padding-left: 30px;
  line-height: 1.7;
}

/* ===== Accordion (for download page) ===== */
.accordion-item {
  border: 1px solid var(--border-light);
  border-radius: var(--radius);
  margin-bottom: 12px;
  overflow: hidden;
}

.accordion-header {
  width: 100%;
  padding: 18px 24px;
  background: var(--bg-card);
  border: none;
  font-size: 16px;
  font-weight: 600;
  color: var(--text);
  cursor: pointer;
  display: flex;
  justify-content: space-between;
  align-items: center;
  transition: background 0.2s;
}

.accordion-header:hover { background: var(--bg-secondary); }

.accordion-header svg { width: 20px; height: 20px; color: var(--text-muted); transition: transform 0.2s; }

.accordion-item.open .accordion-header svg { transform: rotate(180deg); }

.accordion-body {
  max-height: 0;
  overflow: hidden;
  transition: max-height 0.3s ease;
}

.accordion-item.open .accordion-body { max-height: 500px; }

.accordion-body .content {
  padding: 0 24px 20px;
  font-size: 15px;
  color: var(--text-secondary);
  line-height: 1.7;
}

/* ===== Steps ===== */
.steps {
  display: flex;
  gap: 24px;
  counter-reset: step;
}

.step-item {
  flex: 1;
  position: relative;
  padding-top: 40px;
}

.step-item::before {
  counter-increment: step;
  content: counter(step);
  position: absolute;
  top: 0; left: 0;
  width: 32px; height: 32px;
  background: var(--primary);
  color: #fff;
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 14px;
  font-weight: 700;
}

.step-item h4 { font-size: 16px; font-weight: 600; margin-bottom: 6px; }
.step-item p { font-size: 14px; color: var(--text-secondary); line-height: 1.6; }

/* ===== Version Log ===== */
.version-log {
  border-left: 3px solid var(--primary);
  padding-left: 24px;
}

.log-item {
  margin-bottom: 28px;
  position: relative;
}

.log-item::before {
  content: '';
  position: absolute;
  left: -29px; top: 6px;
  width: 10px; height: 10px;
  background: var(--primary);
  border-radius: 50%;
}

.log-item .log-date { font-size: 13px; color: var(--text-muted); margin-bottom: 4px; }
.log-item .log-version { font-size: 16px; font-weight: 600; margin-bottom: 6px; }
.log-item .log-changes { font-size: 14px; color: var(--text-secondary); line-height: 1.6; }

/* ===== Scenes Grid ===== */
.scene-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 24px;
}

.scene-card {
  border-radius: var(--radius-lg);
  overflow: hidden;
  border: 1px solid var(--border-light);
  transition: all 0.25s ease;
}

.scene-card:hover { box-shadow: var(--shadow-hover); }

.scene-card .scene-visual {
  height: 160px;
  background: var(--primary-light);
  display: flex;
  align-items: center;
  justify-content: center;
}

.scene-card .scene-visual svg { width: 64px; height: 64px; color: var(--primary); opacity: 0.6; }

.scene-card .scene-info { padding: 20px; }
.scene-card h4 { font-size: 16px; font-weight: 600; margin-bottom: 6px; }
.scene-card p { font-size: 14px; color: var(--text-secondary); line-height: 1.6; }

/* ===== Safety Banner ===== */
.safety-banner {
  background: linear-gradient(135deg, #e8f5e9 0%, #c8e6c9 100%);
  border-radius: var(--radius-lg);
  padding: 32px;
  display: flex;
  align-items: center;
  gap: 20px;
  margin: 40px 0;
}

.safety-banner svg { width: 48px; height: 48px; color: var(--accent); flex-shrink: 0; }

.safety-banner h3 { font-size: 18px; font-weight: 600; margin-bottom: 4px; }
.safety-banner p { font-size: 15px; color: var(--text-secondary); }

/* ===== CTA Section ===== */
.cta-section {
  background: var(--primary-light);
  border-radius: var(--radius-lg);
  padding: 56px 32px;
  text-align: center;
  margin: 48px 0;
}

.cta-section h2 { font-size: 28px; font-weight: 700; margin-bottom: 12px; }
.cta-section p { font-size: 17px; color: var(--text-secondary); margin-bottom: 24px; }

/* ===== Footer ===== */
footer {
  background: var(--bg-secondary);
  border-top: 1px solid var(--border-light);
  padding: 40px 0;
  margin-top: 64px;
}

.footer-inner {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 24px;
  display: flex;
  justify-content: space-between;
  align-items: center;
  flex-wrap: wrap;
  gap: 16px;
}

.footer-safety {
  display: flex;
  align-items: center;
  gap: 10px;
  font-size: 14px;
  color: var(--accent);
}

.footer-safety svg { width: 18px; height: 18px; }

.footer-copy {
  font-size: 13px;
  color: var(--text-muted);
}

/* ===== Responsive ===== */
@media (max-width: 768px) {
  .hero h1 { font-size: 32px; }
  .hero-subtitle { font-size: 17px; }
  .hero-actions { flex-direction: column; align-items: center; }
  .stats-grid { grid-template-columns: repeat(2, 1fr); }
  .scene-grid { grid-template-columns: 1fr; }
  .steps { flex-direction: column; }
  .section-title { font-size: 26px; }
  .footer-inner { flex-direction: column; text-align: center; }
  nav { padding: 0 16px; }
  .nav-links a { padding: 6px 12px; font-size: 14px; }
}

@media (max-width: 480px) {
  .feature-grid { grid-template-columns: 1fr; }
  .download-grid { grid-template-columns: 1fr; }
  .stats-grid { grid-template-columns: 1fr; }
}

/* ===== Spin animation ===== */
@keyframes spin {
  from { transform: rotate(0deg); }
  to { transform: rotate(360deg); }
}

/* ===== Utility ===== */
.text-center { text-align: center; }
.mb-8 { margin-bottom: 8px; }
.mb-16 { margin-bottom: 16px; }
.mb-24 { margin-bottom: 24px; }
.mt-24 { margin-top: 24px; }
.mt-48 { margin-top: 48px; }
.bg-alt { background: var(--bg-secondary); }