:root {
  --bg: #161719;
  --bg-soft: #1D1E21;
  --surface: #25262B;
  --brand: #4C8DFF;
  --brand-hover: #6FA6FF;
  --text: #E8EAED;
  --text-muted: #9AA0A6;
  --border: #34363C;
  --radius: 12px;
  --maxw: 1120px;
  --font: "PingFang SC", "Microsoft YaHei", "Source Han Sans SC", system-ui, -apple-system, sans-serif;
}

*, *::before, *::after { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  margin: 0;
  font-family: var(--font);
  color: var(--text);
  background: var(--bg);
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
}
a { color: inherit; text-decoration: none; }
img, svg { display: block; max-width: 100%; }
h1, h2, h3, p { margin: 0; }

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

.section { padding: 88px 0; }
.section-soft { background: var(--bg-soft); }
.section-title { font-size: 32px; font-weight: 800; text-align: center; }
.section-subtitle { color: var(--text-muted); text-align: center; margin-top: 12px; }

.btn {
  display: inline-block; padding: 12px 26px; border-radius: 8px;
  font-size: 16px; font-weight: 600; cursor: pointer; transition: all .18s ease;
  border: 1.5px solid transparent;
}
.btn-primary { background: var(--brand); color: #0E1116; }
.btn-primary:hover { background: var(--brand-hover); }
.btn-outline { background: transparent; color: var(--brand); border-color: var(--brand); }
.btn-outline:hover { background: var(--brand); color: #0E1116; }

/* ===== 导航 ===== */
.nav {
  position: sticky; top: 0; z-index: 50;
  background: rgba(22, 23, 25, .8);
  backdrop-filter: saturate(180%) blur(8px);
  border-bottom: 1px solid var(--border);
}
.nav-inner { display: flex; align-items: center; justify-content: space-between; height: 64px; }
.nav-links { display: flex; align-items: center; gap: 28px; }
.nav-links > a { color: var(--text-muted); font-weight: 500; transition: color .15s; }
.nav-links > a:hover, .nav-links > a.active { color: var(--brand); }
.nav-cta { color: #0E1116 !important; padding: 8px 18px; font-size: 15px; }
.nav-toggle { display: none; flex-direction: column; gap: 5px; background: none; border: 0; cursor: pointer; padding: 6px; }
.nav-toggle span { width: 22px; height: 2px; background: var(--text); border-radius: 2px; }

.logo { display: inline-flex; align-items: center; gap: 9px; }
.logo-text { font-size: 22px; font-weight: 800; letter-spacing: .5px; color: var(--text); }

/* ===== Hero ===== */
.hero { padding: 96px 0 72px; background: linear-gradient(180deg, var(--bg) 0%, var(--bg-soft) 100%); }
.hero-inner { text-align: center; }
.hero-title { font-size: 48px; font-weight: 800; line-height: 1.2; }
.hero-sub { font-size: 20px; color: var(--text-muted); margin-top: 18px; }
.hero-cta { display: flex; gap: 16px; justify-content: center; margin-top: 32px; }
.hero-shot {
  margin: 56px auto 0; max-width: 900px; aspect-ratio: 16 / 9;
  background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius);
  box-shadow: 0 24px 60px -28px rgba(0, 0, 0, .6);
  display: flex; align-items: center; justify-content: center; color: var(--text-muted);
}

/* ===== 功能卡 ===== */
.feature-grid { margin-top: 48px; display: grid; gap: 24px; grid-template-columns: repeat(3, 1fr); }
.card {
  background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius);
  padding: 28px; transition: box-shadow .2s, transform .2s;
}
.card:hover { box-shadow: 0 16px 36px -20px rgba(76, 141, 255, .22); transform: translateY(-3px); }
.card-icon {
  width: 48px; height: 48px; border-radius: 10px; background: rgba(76, 141, 255, .12);
  display: flex; align-items: center; justify-content: center; margin-bottom: 18px;
}
.card-title { font-size: 18px; font-weight: 700; }
.card-desc { color: var(--text-muted); margin-top: 10px; font-size: 15px; }

/* ===== 安全子区 ===== */
.security { margin-top: 64px; }
.security-title { font-size: 22px; font-weight: 700; text-align: center; }
.security-list {
  list-style: none; padding: 0; margin: 28px 0 0;
  display: grid; gap: 16px; grid-template-columns: repeat(3, 1fr);
}
.security-list li {
  background: var(--surface); border-radius: 10px; padding: 18px 20px;
  display: flex; flex-direction: column; gap: 6px;
}
.security-list strong { font-size: 15px; }
.security-list span { color: var(--text-muted); font-size: 14px; }

/* ===== 截图 ===== */
.shot-grid { margin-top: 48px; display: grid; gap: 24px; grid-template-columns: repeat(3, 1fr); }
.shot { margin: 0; }
.shot-frame {
  aspect-ratio: 16 / 10; background: var(--surface); border: 1px solid var(--border);
  border-radius: var(--radius); display: flex; align-items: center; justify-content: center;
  color: var(--text-muted); box-shadow: 0 12px 30px -22px rgba(0, 0, 0, .45);
}
.shot figcaption { text-align: center; margin-top: 14px; color: var(--text-muted); font-size: 15px; }

/* ===== 理念 ===== */
.philosophy { text-align: center; }
.philosophy-text { max-width: 720px; margin: 24px auto 0; font-size: 19px; color: var(--text-muted); line-height: 1.9; }

/* ===== 下载 ===== */
.dl-grid { margin-top: 48px; display: grid; gap: 24px; grid-template-columns: repeat(2, 1fr); }
.dl-card { background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius); padding: 32px; }
.dl-card h3 { font-size: 20px; font-weight: 700; }
.dl-card p { color: var(--text-muted); margin-top: 12px; min-height: 48px; }
.dl-actions { display: flex; gap: 12px; margin-top: 22px; flex-wrap: wrap; }

/* ===== 联系 ===== */
.contact { text-align: center; }
.contact-cta { display: flex; gap: 16px; justify-content: center; margin-top: 32px; }
.contact-email { margin-top: 22px; color: var(--text-muted); font-size: 15px; }
.contact-email a { color: var(--brand); }

/* ===== 页脚 ===== */
.footer { border-top: 1px solid var(--border); padding: 36px 0; background: var(--bg-soft); }
.footer-inner { display: flex; align-items: center; justify-content: space-between; gap: 16px; flex-wrap: wrap; }
.footer-brand { font-weight: 800; }
.footer-links { display: flex; gap: 22px; }
.footer-links a { color: var(--text-muted); font-size: 14px; }
.footer-links a:hover { color: var(--brand); }
.footer-copy { color: var(--text-muted); font-size: 13px; }

/* ===== 响应式 ===== */
@media (max-width: 980px) { .feature-grid, .security-list { grid-template-columns: repeat(2, 1fr); } }
@media (max-width: 820px) { .shot-grid { grid-template-columns: 1fr; } }
@media (max-width: 720px) {
  .section { padding: 56px 0; }
  .section-title { font-size: 26px; }
  .nav-toggle { display: flex; }
  .nav-links {
    position: absolute; top: 64px; left: 0; right: 0;
    flex-direction: column; align-items: stretch; gap: 0;
    background: var(--surface); border-bottom: 1px solid var(--border);
    padding: 8px 0; display: none;
  }
  .nav-links.open { display: flex; }
  .nav-links > a { padding: 12px 24px; }
  .nav-cta { margin: 8px 24px; text-align: center; }
  .hero-title { font-size: 32px; }
  .hero-sub { font-size: 17px; }
  .hero-cta { flex-direction: column; align-items: center; }
  .dl-grid { grid-template-columns: 1fr; }
  .contact-cta { flex-direction: column; align-items: center; }
  .footer-inner { flex-direction: column; text-align: center; }
}
@media (max-width: 620px) { .feature-grid, .security-list { grid-template-columns: 1fr; } }