/* ========== 第1套：清爽简约风 - 安全下载中心 ========== */

/* Reset */
*, *::before, *::after { margin: 0; padding: 0; box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", sans-serif;
  line-height: 1.7; color: #333; background: #f8fafc;
}
img, svg { display: block; max-width: 100%; }
a { text-decoration: none; color: inherit; }
button { cursor: pointer; font-family: inherit; border: none; background: none; }
ul, ol { list-style: none; }

/* Variables */
:root {
  --primary: #1a73e8; --primary-dark: #1557b0; --primary-light: #e8f0fe;
  --secondary: #34a853; --accent: #fbbc04; --danger: #ea4335;
  --text: #202124; --text-secondary: #5f6368; --text-muted: #80868b;
  --bg: #f8fafc; --bg-white: #ffffff; --bg-card: #ffffff;
  --border: #dadce0; --shadow: 0 1px 3px rgba(60,64,67,0.08);
  --shadow-lg: 0 4px 12px rgba(60,64,67,0.12);
  --radius: 8px; --radius-lg: 12px;
}

/* Layout */
.container { max-width: 1200px; margin: 0 auto; padding: 0 24px; }
.section { padding: 64px 0; }
.section-alt { background: var(--bg-white); }

/* Navigation - Clean top fixed */
.main-nav {
  position: fixed; top: 0; left: 0; right: 0; z-index: 1000;
  background: rgba(255,255,255,0.95); backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--border);
}
.nav-container { max-width: 1200px; margin: 0 auto; padding: 0 24px; display: flex; align-items: center; justify-content: space-between; height: 60px; }
.nav-brand { display: flex; align-items: center; gap: 10px; font-size: 1.25rem; font-weight: 700; color: var(--text); }
.nav-brand svg { width: 28px; height: 28px; }
.nav-links { display: flex; gap: 4px; }
.nav-links a {
  padding: 8px 18px; border-radius: 20px; font-size: 0.875rem; font-weight: 500;
  color: var(--text-secondary); transition: all 0.2s;
}
.nav-links a:hover { background: var(--primary-light); color: var(--primary); }
.nav-links a.active { background: var(--primary); color: #fff; }

/* Mobile nav */
.nav-toggle { display: none; flex-direction: column; gap: 4px; padding: 8px; }
.nav-toggle span { display: block; width: 22px; height: 2px; background: var(--text); border-radius: 1px; }
@media (max-width: 768px) {
  .nav-toggle { display: flex; }
  .nav-links { display: none; position: absolute; top: 60px; left: 0; right: 0; background: #fff; border-bottom: 1px solid var(--border); padding: 12px 24px; flex-direction: column; gap: 4px; }
  .nav-links.open { display: flex; }
  .nav-links a { padding: 12px 16px; border-radius: var(--radius); }
}

/* Hero */
.hero { padding: 120px 0 80px; background: linear-gradient(180deg, #e8f0fe 0%, #f8fafc 100%); text-align: center; }
.hero h1 { font-size: 2.75rem; font-weight: 800; color: var(--text); margin-bottom: 16px; line-height: 1.2; }
.hero .subtitle { font-size: 1.125rem; color: var(--text-secondary); max-width: 640px; margin: 0 auto 32px; }
.hero-version { display: inline-flex; align-items: center; gap: 16px; margin-bottom: 28px; flex-wrap: wrap; justify-content: center; }
.hero-version span { font-size: 0.8125rem; color: var(--text-muted); display: flex; align-items: center; gap: 6px; }
.hero-version svg { width: 14px; height: 14px; }

/* Buttons */
.btn {
  display: inline-flex; align-items: center; justify-content: center; gap: 8px;
  padding: 14px 32px; border-radius: var(--radius-lg); font-size: 1rem; font-weight: 600;
  transition: all 0.2s; cursor: pointer;
}
.btn-primary { background: var(--primary); color: #fff; box-shadow: 0 2px 8px rgba(26,115,232,0.3); }
.btn-primary:hover { background: var(--primary-dark); transform: translateY(-1px); box-shadow: 0 4px 16px rgba(26,115,232,0.35); }
.btn-secondary { background: var(--bg-white); color: var(--primary); border: 1.5px solid var(--primary); }
.btn-secondary:hover { background: var(--primary-light); }
.btn-lg { padding: 16px 40px; font-size: 1.0625rem; }
.btn svg { width: 20px; height: 20px; }

/* Cards */
.card-grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(300px, 1fr)); gap: 24px; margin-top: 40px; }
.card {
  background: var(--bg-card); border-radius: var(--radius-lg); padding: 32px;
  box-shadow: var(--shadow); border: 1px solid var(--border);
  transition: all 0.2s;
}
.card:hover { box-shadow: var(--shadow-lg); transform: translateY(-2px); }
.card-icon { width: 48px; height: 48px; margin-bottom: 16px; color: var(--primary); }
.card h3 { font-size: 1.125rem; font-weight: 600; color: var(--text); margin-bottom: 10px; }
.card p { font-size: 0.9375rem; color: var(--text-secondary); line-height: 1.7; }

/* Section header */
.section-header { text-align: center; margin-bottom: 48px; }
.section-header h2 { font-size: 2rem; font-weight: 700; color: var(--text); margin-bottom: 12px; }
.section-header p { font-size: 1rem; color: var(--text-secondary); max-width: 560px; margin: 0 auto; }

/* Platform cards */
.platform-grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(200px, 1fr)); gap: 20px; margin-top: 40px; }
.platform-card {
  background: var(--bg-card); border-radius: var(--radius-lg); padding: 28px 20px;
  text-align: center; border: 1.5px solid var(--border); transition: all 0.2s;
}
.platform-card:hover { border-color: var(--primary); box-shadow: var(--shadow-lg); }
.platform-card svg { width: 40px; height: 40px; margin: 0 auto 12px; color: var(--primary); }
.platform-card h4 { font-size: 1rem; font-weight: 600; margin-bottom: 6px; }
.platform-card p { font-size: 0.8125rem; color: var(--text-muted); margin-bottom: 16px; }
.platform-card .btn { padding: 10px 20px; font-size: 0.8125rem; }

/* Feature section */
.feature-block { display: grid; grid-template-columns: 1fr 1fr; gap: 64px; align-items: center; margin-bottom: 64px; }
.feature-block:nth-child(even) { direction: rtl; }
.feature-block:nth-child(even) > * { direction: ltr; }
.feature-block h3 { font-size: 1.5rem; font-weight: 700; color: var(--text); margin-bottom: 16px; }
.feature-block p { font-size: 1rem; color: var(--text-secondary); line-height: 1.8; margin-bottom: 12px; }
.feature-block svg { width: 100%; max-width: 400px; height: auto; }
@media (max-width: 768px) { .feature-block { grid-template-columns: 1fr; gap: 32px; } }

/* Stats */
.stats-grid { display: grid; grid-template-columns: repeat(4, 1fr); gap: 24px; text-align: center; }
.stat-item h4 { font-size: 2.5rem; font-weight: 800; color: var(--primary); margin-bottom: 8px; }
.stat-item p { font-size: 0.9375rem; color: var(--text-secondary); }
@media (max-width: 768px) { .stats-grid { grid-template-columns: repeat(2, 1fr); } }

/* Reviews */
.review-grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(300px, 1fr)); gap: 24px; }
.review-card { background: var(--bg-card); border-radius: var(--radius-lg); padding: 28px; border: 1px solid var(--border); }
.review-stars { display: flex; gap: 4px; margin-bottom: 12px; }
.review-stars svg { width: 18px; height: 18px; color: var(--accent); fill: var(--accent); }
.review-card p { font-size: 0.9375rem; color: var(--text-secondary); line-height: 1.7; margin-bottom: 16px; }
.review-author { font-size: 0.875rem; font-weight: 600; color: var(--text); }

/* Comparison table */
.compare-table { width: 100%; border-collapse: collapse; margin-top: 32px; background: var(--bg-card); border-radius: var(--radius-lg); overflow: hidden; box-shadow: var(--shadow); }
.compare-table th, .compare-table td { padding: 16px 20px; text-align: left; border-bottom: 1px solid var(--border); }
.compare-table th { background: var(--primary-light); font-weight: 600; color: var(--text); }
.compare-table tr:last-child td { border-bottom: none; }
.compare-table td { font-size: 0.9375rem; color: var(--text-secondary); }
.compare-table .check { color: var(--secondary); }
.compare-table .cross { color: var(--danger); }

/* Scenarios */
.scenario-grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(240px, 1fr)); gap: 24px; }
.scenario-card { background: var(--bg-card); border-radius: var(--radius-lg); padding: 28px; text-align: center; border: 1px solid var(--border); }
.scenario-card svg { width: 48px; height: 48px; margin: 0 auto 16px; color: var(--primary); }
.scenario-card h4 { font-size: 1.0625rem; font-weight: 600; margin-bottom: 10px; }
.scenario-card p { font-size: 0.875rem; color: var(--text-secondary); }

/* FAQ */
.faq-list { max-width: 800px; margin: 0 auto; }
.faq-item { border-bottom: 1px solid var(--border); }
.faq-question {
  width: 100%; padding: 20px 0; display: flex; justify-content: space-between; align-items: center;
  font-size: 1rem; font-weight: 500; color: var(--text); cursor: pointer; text-align: left;
}
.faq-question svg { width: 20px; height: 20px; color: var(--text-muted); flex-shrink: 0; transition: transform 0.2s; }
.faq-item.active .faq-question svg { transform: rotate(180deg); }
.faq-answer { max-height: 0; overflow: hidden; transition: max-height 0.3s ease; }
.faq-answer-inner { padding-bottom: 20px; font-size: 0.9375rem; color: var(--text-secondary); line-height: 1.8; }
.faq-item.active .faq-answer { max-height: 500px; }

/* Download page */
.download-hero { padding: 120px 0 60px; background: linear-gradient(180deg, #e8f0fe 0%, #f8fafc 100%); }
.download-main { display: grid; grid-template-columns: 1fr 1fr; gap: 48px; align-items: center; }
.download-main h1 { font-size: 2.25rem; font-weight: 800; margin-bottom: 16px; }
.download-main .meta { display: flex; gap: 20px; margin-bottom: 24px; flex-wrap: wrap; }
.download-main .meta span { font-size: 0.875rem; color: var(--text-muted); display: flex; align-items: center; gap: 6px; }
.download-main .meta svg { width: 14px; height: 14px; }
@media (max-width: 768px) { .download-main { grid-template-columns: 1fr; } }

/* Install steps */
.steps { display: flex; flex-direction: column; gap: 24px; max-width: 800px; margin: 0 auto; }
.step { display: flex; gap: 20px; align-items: flex-start; }
.step-num {
  width: 40px; height: 40px; border-radius: 50%; background: var(--primary); color: #fff;
  display: flex; align-items: center; justify-content: center; font-weight: 700; flex-shrink: 0;
}
.step-content h4 { font-size: 1.0625rem; font-weight: 600; margin-bottom: 8px; }
.step-content p { font-size: 0.9375rem; color: var(--text-secondary); line-height: 1.7; }

/* Version history */
.version-list { max-width: 800px; margin: 0 auto; }
.version-item { display: flex; gap: 24px; padding: 24px 0; border-bottom: 1px solid var(--border); }
.version-item:last-child { border-bottom: none; }
.version-badge { background: var(--primary); color: #fff; padding: 6px 14px; border-radius: 20px; font-size: 0.8125rem; font-weight: 600; white-space: nowrap; }
.version-content h4 { font-size: 1rem; font-weight: 600; margin-bottom: 8px; }
.version-content ul { list-style: disc; padding-left: 18px; }
.version-content li { font-size: 0.9375rem; color: var(--text-secondary); margin-bottom: 6px; }

/* Security badge */
.security-section { background: var(--bg-white); border-radius: var(--radius-lg); padding: 40px; text-align: center; border: 1.5px solid var(--border); }
.security-section svg { width: 64px; height: 64px; margin: 0 auto 20px; color: var(--secondary); }

/* Requirements table */
.req-table { width: 100%; border-collapse: collapse; margin-top: 24px; }
.req-table th, .req-table td { padding: 14px 18px; text-align: left; border: 1px solid var(--border); }
.req-table th { background: #f1f3f4; font-weight: 600; }
.req-table td { font-size: 0.9375rem; color: var(--text-secondary); }

/* CTA Banner */
.cta-banner { background: linear-gradient(135deg, var(--primary) 0%, var(--primary-dark) 100%); border-radius: var(--radius-lg); padding: 48px; text-align: center; color: #fff; }
.cta-banner h3 { font-size: 1.75rem; font-weight: 700; margin-bottom: 12px; }
.cta-banner p { font-size: 1rem; margin-bottom: 24px; opacity: 0.9; }
.cta-banner .btn { background: #fff; color: var(--primary); }

/* Footer */
.main-footer { background: var(--text); color: #bdc1c6; padding: 40px 0 24px; margin-top: 80px; }
.footer-container { max-width: 1200px; margin: 0 auto; padding: 0 24px; }
.footer-top { display: flex; justify-content: space-between; align-items: center; margin-bottom: 24px; flex-wrap: wrap; gap: 16px; }
.footer-brand { display: flex; align-items: center; gap: 10px; font-weight: 700; color: #fff; }
.footer-brand svg { width: 24px; height: 24px; }
.footer-links { display: flex; gap: 24px; }
.footer-links a { font-size: 0.875rem; color: #bdc1c6; transition: color 0.2s; }
.footer-links a:hover { color: #fff; }
.footer-bottom { border-top: 1px solid #3c4043; padding-top: 20px; font-size: 0.8125rem; color: #9aa0a6; line-height: 1.8; }

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

/* Utility */
.text-center { text-align: center; }
.mt-4 { margin-top: 16px; }
.mt-6 { margin-top: 24px; }
.mb-4 { margin-bottom: 16px; }