/* === Site 6: app - Mobile Multi-device Style === */
/* Emphasize Android, iOS, account sync and cross-device experience */

:root {
  --primary: #ff6b35;
  --primary-dark: #e55a2b;
  --primary-light: #fff0eb;
  --accent: #00b894;
  --text: #1e272e;
  --text-secondary: #576574;
  --bg: #ffffff;
  --bg-secondary: #fdfbfb;
  --border: #e8e4e1;
  --shadow: 0 2px 6px rgba(255,107,53,0.06);
  --shadow-hover: 0 8px 24px rgba(255,107,53,0.12);
  --radius: 14px;
  --radius-lg: 22px;
  --max-width: 1200px;
}

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

html { scroll-behavior: smooth; }

body {
  font-family: "SF Pro Display", -apple-system, "Segoe UI", "PingFang SC", "Microsoft YaHei", sans-serif;
  color: var(--text);
  background: var(--bg);
  line-height: 1.7;
  -webkit-font-smoothing: antialiased;
}

/* --- Navigation --- */
.site-header {
  background: rgba(255,255,255,0.92);
  backdrop-filter: blur(16px);
  border-bottom: 1px solid var(--border);
  position: sticky;
  top: 0;
  z-index: 100;
}

.nav-container {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 24px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 66px;
}

.nav-brand {
  display: flex;
  align-items: center;
  gap: 10px;
  font-size: 19px;
  font-weight: 700;
  color: var(--text);
  text-decoration: none;
}

.nav-brand svg {
  width: 30px;
  height: 30px;
}

.nav-menu {
  display: flex;
  list-style: none;
  gap: 6px;
}

.nav-menu a {
  display: block;
  padding: 10px 22px;
  text-decoration: none;
  color: var(--text-secondary);
  font-size: 15px;
  font-weight: 500;
  border-radius: 100px;
  transition: all 0.3s ease;
  position: relative;
}

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

.nav-menu a.active {
  background: var(--primary);
  color: #fff;
  box-shadow: 0 2px 12px rgba(255,107,53,0.3);
}

/* --- Hero --- */
.hero {
  background: linear-gradient(160deg, #fdfbfb 0%, #fff0eb 40%, #ffe8e0 70%, #fdfbfb 100%);
  padding: 72px 24px 64px;
  text-align: center;
  position: relative;
}

.hero::after {
  content: '';
  position: absolute;
  bottom: 0;
  left: 50%;
  transform: translateX(-50%);
  width: 120px;
  height: 4px;
  background: linear-gradient(90deg, var(--primary), var(--accent));
  border-radius: 100px;
}

.hero-container {
  max-width: var(--max-width);
  margin: 0 auto;
  position: relative;
  z-index: 1;
}

.hero h1 {
  font-size: 46px;
  font-weight: 800;
  color: var(--text);
  margin-bottom: 16px;
  line-height: 1.15;
}

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

.hero-subtitle {
  font-size: 19px;
  color: var(--text-secondary);
  max-width: 580px;
  margin: 0 auto 40px;
}

.hero-actions {
  display: flex;
  gap: 14px;
  justify-content: center;
  flex-wrap: wrap;
}

/* --- Buttons --- */
.btn {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 16px 36px;
  border-radius: 100px;
  font-size: 16px;
  font-weight: 600;
  cursor: pointer;
  border: none;
  text-decoration: none;
  transition: all 0.3s ease;
}

.btn-primary {
  background: linear-gradient(135deg, var(--primary), var(--primary-dark));
  color: #fff;
  box-shadow: 0 4px 20px rgba(255,107,53,0.3);
}

.btn-primary:hover {
  transform: translateY(-2px);
  box-shadow: 0 8px 28px rgba(255,107,53,0.4);
}

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

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

.btn svg {
  width: 18px;
  height: 18px;
  flex-shrink: 0;
}

/* --- Sections --- */
.section {
  padding: 72px 24px;
}

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

.section-container {
  max-width: var(--max-width);
  margin: 0 auto;
}

.section-header {
  text-align: center;
  margin-bottom: 52px;
}

.section-header h2 {
  font-size: 36px;
  font-weight: 700;
  color: var(--text);
  margin-bottom: 12px;
}

.section-header p {
  font-size: 17px;
  color: var(--text-secondary);
  max-width: 520px;
  margin: 0 auto;
}

/* --- Device Cards --- */
.device-showcase {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: 28px;
  margin-bottom: 48px;
}

.device-card {
  background: var(--bg);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 36px;
  text-align: center;
  transition: all 0.35s ease;
}

.device-card:hover {
  box-shadow: var(--shadow-hover);
  border-color: rgba(255,107,53,0.25);
  transform: translateY(-4px);
}

.device-card .device-icon {
  width: 72px;
  height: 72px;
  background: linear-gradient(135deg, var(--primary-light), #fff);
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  margin: 0 auto 20px;
}

.device-card .device-icon svg {
  width: 34px;
  height: 34px;
  color: var(--primary);
}

.device-card h3 {
  font-size: 20px;
  font-weight: 600;
  margin-bottom: 8px;
}

.device-card p {
  font-size: 15px;
  color: var(--text-secondary);
  margin-bottom: 20px;
  line-height: 1.7;
}

/* --- Cards --- */
.card-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: 24px;
}

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

.card:hover {
  box-shadow: var(--shadow-hover);
  border-color: rgba(255,107,53,0.2);
}

.card-icon {
  width: 52px;
  height: 52px;
  background: var(--primary-light);
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  margin-bottom: 20px;
}

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

.card h3 {
  font-size: 19px;
  font-weight: 600;
  margin-bottom: 10px;
}

.card p {
  font-size: 15px;
  color: var(--text-secondary);
  line-height: 1.75;
}

/* --- Platform Cards --- */
.platform-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(180px, 1fr));
  gap: 20px;
}

.platform-card {
  background: var(--bg);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 28px;
  text-align: center;
  transition: all 0.3s ease;
}

.platform-card:hover {
  box-shadow: var(--shadow-hover);
  border-color: var(--primary);
  transform: translateY(-3px);
}

.platform-card svg {
  width: 40px;
  height: 40px;
  margin-bottom: 14px;
  color: var(--primary);
}

.platform-card h4 {
  font-size: 16px;
  font-weight: 600;
  margin-bottom: 6px;
}

.platform-card p {
  font-size: 13px;
  color: var(--text-secondary);
}

/* --- Stats --- */
.stats-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
  gap: 28px;
  text-align: center;
}

.stat-item h3 {
  font-size: 44px;
  font-weight: 800;
  color: var(--primary);
  line-height: 1;
}

.stat-item p {
  font-size: 15px;
  color: var(--text-secondary);
  margin-top: 10px;
}

/* --- Download Section --- */
.download-hero {
  background: linear-gradient(135deg, var(--primary-dark), var(--primary));
  color: #fff;
  padding: 72px 24px;
  text-align: center;
}

.download-hero h1 {
  font-size: 42px;
  font-weight: 800;
  margin-bottom: 14px;
}

.download-hero p {
  font-size: 18px;
  opacity: 0.9;
  max-width: 560px;
  margin: 0 auto 36px;
}

.download-hero .btn-primary {
  background: #fff;
  color: var(--primary);
  box-shadow: 0 4px 16px rgba(0,0,0,0.15);
}

/* --- Platform Downloads --- */
.platform-downloads {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
  gap: 24px;
}

.platform-download-card {
  background: var(--bg);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 32px;
  display: flex;
  flex-direction: column;
}

.platform-download-card h3 {
  font-size: 19px;
  font-weight: 600;
  margin-bottom: 10px;
  display: flex;
  align-items: center;
  gap: 10px;
}

.platform-download-card h3 svg {
  width: 24px;
  height: 24px;
  color: var(--primary);
}

.platform-download-card .meta {
  font-size: 13px;
  color: var(--text-secondary);
  margin-bottom: 18px;
}

.platform-download-card .btn {
  margin-top: auto;
  padding: 12px 24px;
  font-size: 14px;
  align-self: flex-start;
}

/* --- Steps --- */
.steps {
  display: flex;
  gap: 24px;
  flex-wrap: wrap;
}

.step {
  flex: 1;
  min-width: 220px;
  background: var(--bg);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 28px;
}

.step-num {
  width: 44px;
  height: 44px;
  background: linear-gradient(135deg, var(--primary), var(--primary-dark));
  color: #fff;
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  font-weight: 700;
  font-size: 17px;
  margin-bottom: 16px;
}

.step h4 {
  font-size: 17px;
  font-weight: 600;
  margin-bottom: 8px;
}

.step p {
  font-size: 14px;
  color: var(--text-secondary);
  line-height: 1.75;
}

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

.faq-item summary {
  list-style: none;
  cursor: pointer;
  font-size: 17px;
  font-weight: 600;
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 16px;
}

.faq-item summary::after {
  content: '+';
  font-size: 24px;
  color: var(--primary);
  flex-shrink: 0;
}

.faq-item[open] summary::after {
  content: '−';
}

.faq-item p {
  font-size: 15px;
  color: var(--text-secondary);
  line-height: 1.8;
  margin-top: 12px;
  padding-right: 32px;
}

/* --- Changelog --- */
.changelog-item {
  padding: 20px 0;
  border-bottom: 1px solid var(--border);
  display: flex;
  gap: 24px;
}

.changelog-date {
  font-size: 14px;
  font-weight: 600;
  color: var(--primary);
  white-space: nowrap;
  min-width: 100px;
}

.changelog-content h4 {
  font-size: 16px;
  font-weight: 600;
  margin-bottom: 6px;
}

.changelog-content ul {
  font-size: 14px;
  color: var(--text-secondary);
  padding-left: 18px;
  line-height: 1.8;
}

/* --- Article --- */
.article-content {
  max-width: 760px;
  margin: 0 auto;
  font-size: 16px;
  line-height: 1.8;
}

.article-content h2 {
  font-size: 24px;
  font-weight: 700;
  margin: 36px 0 14px;
  color: var(--primary-dark);
}

.article-content h3 {
  font-size: 19px;
  font-weight: 600;
  margin: 24px 0 10px;
  color: var(--text);
}

.article-content p {
  margin-bottom: 16px;
}

.article-content ol,
.article-content ul {
  margin-bottom: 16px;
  padding-left: 26px;
}

.tip-box {
  background: var(--primary-light);
  border-radius: var(--radius);
  padding: 16px 20px;
  margin: 20px 0;
  font-size: 15px;
  border: 1px solid #ffd5c8;
}

/* --- Footer --- */
.site-footer {
  background: var(--bg-secondary);
  border-top: 1px solid var(--border);
  padding: 44px 24px;
  text-align: center;
}

.footer-container {
  max-width: var(--max-width);
  margin: 0 auto;
}

.footer-badge {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  color: var(--accent);
  font-size: 14px;
  font-weight: 600;
  margin-bottom: 12px;
}

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

.footer-copyright {
  font-size: 13px;
  color: var(--text-secondary);
  line-height: 1.7;
}

/* --- Animations --- */
@keyframes spin {
  from { transform: rotate(0deg); }
  to { transform: rotate(360deg); }
}

/* --- Responsive --- */
@media (max-width: 768px) {
  .hero h1 { font-size: 32px; }
  .hero-subtitle { font-size: 17px; }
  .section-header h2 { font-size: 28px; }
  .nav-container { padding: 0 16px; }
  .nav-menu a { padding: 8px 16px; font-size: 14px; }
  .section { padding: 56px 16px; }
  .hero { padding: 56px 16px 48px; }
  .download-hero h1 { font-size: 32px; }
  .stats-grid { grid-template-columns: repeat(2, 1fr); }
  .steps { flex-direction: column; }
  .device-showcase { grid-template-columns: 1fr; }
  .changelog-item { flex-direction: column; gap: 8px; }
}