:root {
  --bg-main: #f8fafc;
  --bg-card: #ffffff;
  --text-primary: #0f172a;
  --text-secondary: #475569;
  --text-muted: #94a3b8;
  --primary: #2563eb;
  --primary-light: #eff6ff;
  --accent: #0284c7;
  --success: #16a34a;
  --success-bg: #f0fdf4;
  --border: #e2e8f0;
  --shadow-sm: 0 1px 3px rgba(0,0,0,0.05);
  --shadow-md: 0 10px 25px -5px rgba(37,99,235,0.08), 0 8px 10px -6px rgba(0,0,0,0.03);
  --shadow-hover: 0 20px 30px -10px rgba(37,99,235,0.15);
  --radius: 16px;
}
* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
}
body {
  background-color: var(--bg-main);
  color: var(--text-primary);
  line-height: 1.6;
  overflow-x: hidden;
}
a {
  text-decoration: none;
  color: inherit;
}
.header {
  position: sticky;
  top: 0;
  z-index: 100;
  background: rgba(255, 255, 255, 0.85);
  backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--border);
}
.container {
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 24px;
}
.nav-wrapper {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 72px;
}
.logo {
  display: flex;
  align-items: center;
  gap: 10px;
  font-size: 20px;
  font-weight: 800;
  color: var(--primary);
  letter-spacing: -0.5px;
}
.logo-icon {
  width: 32px;
  height: 32px;
  background: linear-gradient(135deg, var(--primary), var(--accent));
  border-radius: 8px;
  display: flex;
  align-items: center;
  justify-content: center;
  color: #fff;
  font-weight: bold;
}
.tag-badge {
  font-size: 12px;
  padding: 2px 8px;
  background: var(--primary-light);
  color: var(--primary);
  border-radius: 20px;
  font-weight: 600;
  margin-left: 6px;
}
.nav-links {
  display: flex;
  align-items: center;
  gap: 32px;
  list-style: none;
}
.nav-links a {
  font-size: 15px;
  font-weight: 500;
  color: var(--text-secondary);
  transition: color 0.2s;
}
.nav-links a:hover, .nav-links a.active {
  color: var(--primary);
  font-weight: 600;
}
.nav-btn {
  background: var(--primary);
  color: #fff !important;
  padding: 9px 20px;
  border-radius: 10px;
  transition: transform 0.2s, box-shadow 0.2s;
  box-shadow: 0 4px 12px rgba(37, 99, 235, 0.2);
}
.nav-btn:hover {
  transform: translateY(-1px);
  box-shadow: 0 6px 16px rgba(37, 99, 235, 0.3);
}

/* 页面标题 */
.page-title-sec {
  padding: 56px 0 32px;
  text-align: center;
}
.page-title {
  font-size: 36px;
  font-weight: 800;
  color: var(--text-primary);
  letter-spacing: -0.5px;
  margin-bottom: 12px;
}
.page-subtitle {
  font-size: 16px;
  color: var(--text-secondary);
  max-width: 600px;
  margin: 0 auto;
}

/* 设备自检推荐 */
.device-detect {
  margin-bottom: 48px;
}
.device-detect-card {
  background: linear-gradient(135deg, #eff6ff, #ffffff);
  border: 1px solid #bfdbfe;
  border-radius: var(--radius);
  padding: 28px 32px;
  display: flex;
  align-items: center;
  gap: 24px;
  flex-wrap: wrap;
}
.device-detect-icon {
  font-size: 48px;
}
.device-detect-info {
  flex: 1;
  min-width: 220px;
}
.device-detect-label {
  font-size: 13px;
  color: var(--text-muted);
  letter-spacing: 0.5px;
  text-transform: uppercase;
}
.device-detect-title {
  font-size: 26px;
  font-weight: 800;
  margin: 4px 0 8px;
}
.device-detect-desc {
  font-size: 14px;
  color: var(--text-secondary);
  max-width: 480px;
}
.btn-detect {
  white-space: nowrap;
}

/* 下载卡片 */
.download-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
  gap: 24px;
  margin-bottom: 60px;
}
.download-card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 32px 24px;
  text-align: center;
  box-shadow: var(--shadow-sm);
  transition: all 0.3s;
  display: flex;
  flex-direction: column;
  align-items: center;
}
.download-card:hover {
  transform: translateY(-6px);
  box-shadow: var(--shadow-hover);
  border-color: #bfdbfe;
}
.platform-icon {
  font-size: 48px;
  margin-bottom: 16px;
}
.platform-name {
  font-size: 22px;
  font-weight: 700;
  margin-bottom: 6px;
}
.platform-info {
  font-size: 13px;
  color: var(--text-muted);
  margin-bottom: 24px;
  line-height: 1.8;
}
.secure-tag {
  display: inline-block;
  margin-top: 6px;
  background: var(--success-bg);
  color: var(--success);
  font-size: 11px;
  font-weight: 600;
  padding: 2px 10px;
  border-radius: 20px;
}
.btn-download {
  display: inline-block;
  width: 100%;
  padding: 12px 0;
  background: linear-gradient(135deg, #2563eb, #1d4ed8);
  color: #fff;
  border-radius: 10px;
  font-weight: 600;
  font-size: 15px;
  box-shadow: 0 4px 12px rgba(37, 99, 235, 0.2);
  transition: all 0.2s;
  margin-top: auto;
}
.btn-download:hover {
  transform: translateY(-2px);
  box-shadow: 0 6px 18px rgba(37, 99, 235, 0.3);
}

/* 安全验证标志区 */
.trust-badges {
  padding: 48px 0;
}
.badges-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
  gap: 20px;
}
.badge-card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 24px;
  text-align: center;
  transition: all 0.25s;
}
.badge-card:hover {
  border-color: #bfdbfe;
  box-shadow: var(--shadow-md);
}
.badge-icon {
  font-size: 32px;
  display: block;
  margin-bottom: 12px;
}
.badge-title {
  font-size: 16px;
  font-weight: 700;
  margin-bottom: 8px;
}
.badge-desc {
  font-size: 13px;
  color: var(--text-secondary);
  line-height: 1.6;
}

/* 同步更新说明 */
.sync-update {
  padding: 48px 0;
}
.sync-update-card {
  display: flex;
  align-items: center;
  gap: 24px;
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 28px 32px;
  flex-wrap: wrap;
}
.sync-update-icon {
  font-size: 40px;
}
.sync-update-text {
  flex: 1;
  min-width: 240px;
}
.sync-update-title {
  font-size: 20px;
  font-weight: 700;
  margin-bottom: 6px;
}
.sync-update-desc {
  font-size: 14px;
  color: var(--text-secondary);
}
.text-link {
  color: var(--primary);
  font-weight: 600;
  white-space: nowrap;
}

/* 三步安装 */
.steps-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
  gap: 20px;
}
.step-card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 28px;
  transition: all 0.25s;
}
.step-card:hover {
  background: var(--primary-light);
  border-color: #93c5fd;
}
.step-index {
  font-size: 28px;
  font-weight: 800;
  color: var(--primary);
  margin-bottom: 12px;
}
.step-title {
  font-size: 18px;
  font-weight: 700;
  margin-bottom: 8px;
}
.step-desc {
  font-size: 14px;
  color: var(--text-secondary);
  line-height: 1.6;
}

/* 版本表格 */
.feature-list-sec {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 40px;
  margin-bottom: 60px;
}
.sec-title-sm {
  font-size: 22px;
  font-weight: 700;
  margin-bottom: 20px;
}
.specs-table {
  width: 100%;
  border-collapse: collapse;
}
.specs-table th, .specs-table td {
  padding: 14px 16px;
  text-align: left;
  border-bottom: 1px solid var(--border);
  font-size: 14px;
}
.specs-table th {
  background: var(--primary-light);
  color: var(--primary);
  font-weight: 700;
}

/* FAQ */
.faq-list {
  max-width: 800px;
  margin: 0 auto;
  display: flex;
  flex-direction: column;
  gap: 12px;
}
.faq-item {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 16px 20px;
  transition: border-color 0.2s;
}
.faq-item[open] {
  border-color: var(--primary);
}
.faq-question {
  font-weight: 600;
  cursor: pointer;
  list-style: none;
  position: relative;
  padding-right: 24px;
}
.faq-question::after {
  content: "+";
  position: absolute;
  right: 0;
  top: 50%;
  transform: translateY(-50%);
  font-weight: 700;
  color: var(--primary);
}
.faq-item[open] .faq-question::after {
  content: "−";
}
.faq-answer {
  margin-top: 12px;
  font-size: 14px;
  color: var(--text-secondary);
  line-height: 1.6;
}

/* Footer */
.footer {
  background: #ffffff;
  border-top: 1px solid var(--border);
  padding: 48px 0 24px;
  margin-top: 60px;
}
.footer-grid {
  display: grid;
  grid-template-columns: 2fr repeat(3, 1fr);
  gap: 40px;
  margin-bottom: 40px;
}
.footer-brand-desc {
  font-size: 14px;
  color: var(--text-muted);
  margin-top: 12px;
  max-width: 320px;
}
.footer-heading {
  font-size: 14px;
  font-weight: 700;
  color: var(--text-primary);
  margin-bottom: 16px;
}
.footer-links {
  list-style: none;
}
.footer-links li {
  margin-bottom: 10px;
}
.footer-links a {
  font-size: 14px;
  color: var(--text-secondary);
  transition: color 0.2s;
}
.footer-links a:hover {
  color: var(--primary);
}

/* 页脚下拉工具区 */
.footer-tools {
  margin-bottom: 24px;
  display: flex;
  justify-content: flex-end;
}
.footer-select {
  position: relative;
  min-width: 240px;
  max-width: 320px;
  width: 100%;
}
.footer-select-btn {
  width: 100%;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 8px;
  background: var(--bg-main);
  border: 1px solid var(--border);
  border-radius: 10px;
  padding: 10px 16px;
  font-size: 13px;
  font-weight: 600;
  color: var(--text-secondary);
  cursor: pointer;
  transition: border-color 0.2s, box-shadow 0.2s;
}
.footer-select-btn:hover {
  border-color: var(--primary);
  box-shadow: 0 2px 8px rgba(37,99,235,0.1);
}
.footer-select-dropdown {
  display: none;
  position: absolute;
  bottom: calc(100% + 8px);
  left: 0;
  right: 0;
  max-height: 260px;
  overflow-y: auto;
  background: #ffffff;
  border: 1px solid var(--border);
  border-radius: 10px;
  box-shadow: 0 12px 28px rgba(0,0,0,0.12);
  z-index: 20;
}
.footer-select:hover .footer-select-dropdown,
.footer-select:focus-within .footer-select-dropdown {
  display: block;
}
.footer-select-dropdown a {
  display: block;
  padding: 8px 16px;
  font-size: 13px;
  color: var(--text-secondary);
  transition: background 0.15s, color 0.15s;
}
.footer-select-dropdown a:hover {
  background: var(--primary-light);
  color: var(--primary);
}
.footer-select-dropdown a + a {
  border-top: 1px solid var(--border);
}

/* Footer bottom */
.footer-bottom {
  text-align: center;
  padding-top: 24px;
  border-top: 1px solid var(--border);
  font-size: 13px;
  color: var(--text-muted);
}

/* Responsive */
@media (max-width: 768px) {
  .page-title { font-size: 28px; }
  .nav-links { display: none; }
  .footer-grid { grid-template-columns: 1fr; }
  .footer-tools { justify-content: flex-start; }
  .device-detect-card { flex-direction: column; text-align: center; }
  .sync-update-card { flex-direction: column; text-align: center; }
  .feature-list-sec { padding: 20px; }
}