/* 基础（默认：浅色） */
:root {
  --bg: #f7f9fc;
  --text: #1b2430;
  --muted: #5d6a7b;
  --card: #ffffff;
  --border: #00000014;
  --brand: #1e66ff;
  --accent: #4caf50;
  --shadow: 0 10px 24px rgba(0,0,0,.12);
}
html { color-scheme: light; }

/* auto：系统深色时 */
@media (prefers-color-scheme: dark) {
  :root:not([data-theme]) {
    --bg: #0c1222;
    --text: #e9eef8;
    --muted: #aab3c2;
    --card: rgba(255,255,255,.08);
    --border: rgba(255,255,255,.12);
    --brand: #58a6ff;
    --accent: #4caf50;
    --shadow: 0 10px 32px rgba(0,0,0,.35);
  }
  html:not([data-theme]) { color-scheme: dark; }
}

/* 强制浅色 */
:root[data-theme="light"] {
  --bg: #f7f9fc;
  --text: #1b2430;
  --muted: #5d6a7b;
  --card: #ffffff;
  --border: #00000014;
  --brand: #1e66ff;
  --accent: #4caf50;
  --shadow: 0 10px 24px rgba(0,0,0,.12);
}
html[data-theme="light"] { color-scheme: light; }

/* 强制深色 */
:root[data-theme="dark"] {
  --bg: #0c1222;
  --text: #e9eef8;
  --muted: #aab3c2;
  --card: rgba(255,255,255,.08);
  --border: rgba(255,255,255,.12);
  --brand: #58a6ff;
  --accent: #4caf50;
  --shadow: 0 10px 32px rgba(0,0,0,.35);
}
html[data-theme="dark"] { color-scheme: dark; }

*{box-sizing:border-box}
html,body{height:100%}
body{
  margin:0;
  font-family: system-ui,-apple-system,"Segoe UI",Roboto,Ubuntu,"Helvetica Neue",Arial;
  color:var(--text);
  background:
    radial-gradient(1200px 600px at 10% -10%, #1b2a4b 0%, transparent 50%),
    radial-gradient(1200px 600px at 90% 110%, #13223d 0%, transparent 50%),
    var(--bg);
}

/* 头部导航 */
.site-header{position:sticky;top:0;z-index:10;backdrop-filter:saturate(140%) blur(6px)}
.nav{
  max-width:1100px;margin:0 auto;padding:12px 16px;
  display:flex;align-items:center;justify-content:space-between;
}
.brand{display:flex;align-items:center;gap:10px;color:var(--text);text-decoration:none}
.brand-logo{font-size:22px}
.brand-name{font-weight:700;letter-spacing:.3px}

.nav-actions{display:flex;gap:8px}
.btn{
  appearance:none;border:1px solid var(--border);background:transparent;color:var(--text);
  padding:8px 12px;border-radius:12px;cursor:pointer;text-decoration:none;line-height:1;
}
.btn:hover{border-color:#ffffff33}
.btn.primary{background:var(--accent);border-color:transparent;color:#05220e;font-weight:700}
.btn.primary:hover{filter:brightness(.96)}
.btn.lg{padding:12px 16px;border-radius:14px}
.btn.ghost{background:transparent}

/* 首屏 */
.hero{display:grid;place-items:center;min-height:70vh;padding:24px 16px}
.hero-inner{
  width:100%;max-width:1000px;background:linear-gradient(180deg,#ffffff0f,#ffffff06);
  border:1px solid var(--border);border-radius:24px;padding:36px;box-shadow:var(--shadow);
}
.hero-title{margin:0 0 8px;font-size:clamp(24px,5vw,40px);letter-spacing:.5px}
.hero-sub{margin:0;color:var(--muted);font-size:clamp(14px,2.5vw,18px)}
.cta{display:flex;gap:12px;margin-top:20px;flex-wrap:wrap}

/* 功能网格 */
.features{
  margin:28px auto 0;display:grid;gap:16px;
  grid-template-columns:repeat(4,minmax(200px,1fr));
}
.feature{
  background:var(--card);border:1px solid var(--border);border-radius:16px;padding:18px;
}
.feature .icon{font-size:24px;margin-bottom:8px}
.feature h3{margin:0 0 6px;font-size:16px}
.feature p{margin:0;color:var(--muted);font-size:14px;line-height:1.65}

/* 页脚 */
.site-footer{border-top:1px solid var(--border);margin-top:28px}
.site-footer .footer-meta{
  max-width:1100px;margin:0 auto;padding:16px;color:var(--muted);text-align:center;
}
.site-footer .beian{
  max-width:1100px;margin:0 auto 12px; padding:0 16px 12px;
  display:flex;flex-wrap:wrap;gap:6px;align-items:center;justify-content:center;
  color:var(--muted);font-size:12.5px;
}
.site-footer .beian a{color:inherit;text-decoration:none}
.site-footer .beian a:hover{text-decoration:underline}
.site-footer .beian .sep{opacity:.45}

/* 无障碍：键盘焦点 */
:focus-visible{outline:2px solid var(--brand);outline-offset:2px;border-radius:10px}

/* 响应式 */
@media (max-width:1024px){ .features{grid-template-columns:repeat(2,1fr)} }
@media (max-width:560px){
  .hero-inner{padding:22px;border-radius:18px}
  .features{grid-template-columns:1fr}
  .nav-actions .btn{padding:8px 10px}
  .site-footer .beian{font-size:12px}
}

/* 浅色模式（用户显式偏好） */
@media (prefers-color-scheme: light) {
  :root{
    --bg: #f7f9fc;
    --text:#1b2430;
    --muted:#5d6a7b;
    --card:#ffffff;
    --border:#00000014;
    --shadow: 0 10px 24px rgba(0,0,0,.12);
  }
  .btn.primary{color:#063313}
}