:root{
  --bg:#FAFAFA;--surface:#FFFFFF;--text:#111111;--text-2:#5A5A66;--text-3:#8B8B96;
  --border:#EAEAEA;--border-strong:#D8D8DE;--accent:#3184EE;--accent-soft:rgba(49,132,238,.08);
  --shadow-sm:0 1px 2px rgba(17,17,17,.04);--shadow-md:0 8px 24px rgba(17,17,17,.06);
  --radius:14px;--radius-sm:10px;--radius-pill:999px;--nav-h:64px;--max:1180px;
  --font:'Inter',-apple-system,BlinkMacSystemFont,'Segoe UI',sans-serif;
  --mono:'JetBrains Mono',ui-monospace,Menlo,monospace;
}
[data-theme="dark"]{--bg:#0B0B0F;--surface:#14141B;--text:#ECECF1;--text-2:#A0A0AE;--text-3:#6E6E7A;--border:rgba(255,255,255,.08);--border-strong:rgba(255,255,255,.16);--accent:#3184EE;--accent-soft:rgba(49,132,238,.16);--shadow-sm:0 1px 2px rgba(0,0,0,.4);--shadow-md:0 8px 24px rgba(0,0,0,.4);}
*{box-sizing:border-box;margin:0;padding:0}
html{scroll-behavior:smooth}
body{font-family:var(--font);background:var(--bg);color:var(--text);line-height:1.6;-webkit-font-smoothing:antialiased;transition:background .3s,color .3s;padding-top:var(--nav-h)}
a{color:inherit;text-decoration:none} img{max-width:100%;display:block}
.container{max-width:var(--max);margin:0 auto;padding:0 24px}

/* NAV */
.nav{
  position:fixed;top:0;left:0;right:0;
  height:var(--nav-h);z-index:100;
  display:flex;align-items:center;
  background:var(--bg);                         /* 新增：常态可见 */
  border-bottom:1px solid var(--border);        /* 新增：常态有分隔线 */
  transition:background .3s,border-color .3s,backdrop-filter .3s;
}
@media (max-width:680px){
  :root{ --nav-h:46px; }
}
.nav.scrolled{background:color-mix(in srgb,var(--bg) 80%,transparent);backdrop-filter:saturate(180%) blur(16px);-webkit-backdrop-filter:saturate(180%) blur(16px);border-bottom-color:var(--border)}
.nav-inner{width:100%;max-width:var(--max);margin:0 auto;padding:0 24px;display:flex;align-items:center;gap:36px}
.brand{font-family:var(--mono);font-weight:700;font-size:16px;letter-spacing:-.5px;display:flex;align-items:center;gap:8px;height:40px}
.brand img{height:32px;width:auto;display:block;object-fit:contain;transition:transform .25s}
.brand:hover img{transform:scale(1.05)}
.menu{display:flex;gap:6px;align-items:center;flex:1}
.menu a,.menu .has-dd>button{font-size:14px;font-weight:500;color:var(--text-2);padding:8px 12px;border-radius:8px;background:none;border:none;cursor:pointer;line-height: 1; font-family:inherit;display:flex;align-items:center;gap:4px;transition:color .2s,background .2s}
.menu a:hover,.menu .has-dd>button:hover,.menu a.active{color:var(--text);background:var(--accent-soft)}
.has-dd{position:relative}
.dd-caret{font-size:10px;opacity:.6;transition:transform .2s}
.has-dd[aria-expanded="true"] .dd-caret{transform:rotate(180deg)}
.dropdown{position:absolute;top:calc(100% + 8px);left:0;min-width:240px;background:var(--surface);border:1px solid var(--border);border-radius:var(--radius);box-shadow:var(--shadow-md);padding:6px;opacity:0;visibility:hidden;transform:translateY(-4px);transition:all .2s}
.has-dd[aria-expanded="true"] .dropdown{opacity:1;visibility:visible;transform:translateY(0)}
.dd-item{display:flex;flex-direction:column;padding:10px 12px;border-radius:8px;transition:background .15s}
.dd-item:hover{background:var(--accent-soft)}
.dd-item .t{font-size:14px;font-weight:600;color:var(--text)}
.dd-item .d{font-size:12px;color:var(--text-3);margin-top:2px}
.nav-cta{display:flex;align-items:center;gap:10px}
.btn{display:inline-flex;align-items:center;gap:6px;font-family:inherit;font-size:14px;font-weight:500;padding:9px 16px;border-radius:var(--radius-pill);border:1px solid var(--border-strong);background:var(--surface);color:var(--text);cursor:pointer;transition:all .2s}
.btn:hover{transform:translateY(-1px);box-shadow:var(--shadow-sm);border-color:var(--text-3)}
.btn-primary{background:var(--text);color:var(--bg);border-color:var(--text)}
.btn-primary:hover{background:var(--accent);border-color:var(--accent);color:#fff}
.btn-accent{background:var(--accent);color:#fff;border-color:var(--accent)}
.icon-btn{width:36px;height:36px;display:inline-flex;align-items:center;justify-content:center;border-radius:50%;border:1px solid var(--border);background:var(--surface);cursor:pointer;color:var(--text-2);font-size:14px;transition:all .2s}
.icon-btn:hover{color:var(--text);border-color:var(--text-3)}
.menu-toggle{display:none}
footer{border-top:1px solid var(--border);padding:40px 0;margin-top:60px}
.foot{display:flex;justify-content:space-between;align-items:center;flex-wrap:wrap;gap:16px;font-size:13px;color:var(--text-3)}
.foot-links{display:flex;gap:20px}
.foot-links a:hover{color:var(--text)}

@media (max-width:680px){
  .menu{position:fixed;top:var(--nav-h);left:0;right:0;background:var(--surface);border-bottom:1px solid var(--border);padding:12px;flex-direction:column;align-items:stretch;gap:2px;transform:translateY(-120%);transition:transform .3s;box-shadow:var(--shadow-md)}
  .menu.open{transform:translateY(0)}
  .menu a,.menu .has-dd>button{padding:12px 14px;width:100%;justify-content:space-between}
  .dropdown{position:static;opacity:1;visibility:visible;transform:none;box-shadow:none;border:none;padding:0 0 0 12px;display:none}
  .has-dd[aria-expanded="true"] .dropdown{display:block}
  .menu-toggle{display:inline-flex}
}
/* language visibility */
[data-lang="zh"] [data-i18n="en"] { display: none !important; }
[data-lang="en"] [data-i18n="zh"] { display: none !important; }