/* 共享导航样式 —— 全站统一来源（index.html + 各子页共用） */
.topnav{position:sticky;top:0;z-index:50;background:#0b1220;border-bottom:1px solid #1e293b}
.nav-in{max-width:1100px;margin:0 auto;display:flex;align-items:center;gap:18px;padding:10px 18px}
.topnav .brand{color:#fff;font-size:16px;text-decoration:none;font-weight:600;letter-spacing:.5px}
.topnav .brand b{color:#34d399}
.nav-links{margin-left:auto;display:flex;gap:4px;flex-wrap:wrap}
.nav-links a{color:#f8fafc;text-decoration:none;font-size:13px;padding:5px 10px}
.nav-links a:hover{color:#34d399}
.nav-links a.cur{color:#34d399;font-weight:600}
.nav-toggle{display:none;background:none;border:none;color:#f8fafc;font-size:22px;cursor:pointer;margin-left:auto;padding:4px 8px}
@media(max-width:640px){
  .nav-toggle{display:block}
  .nav-links{display:none;position:absolute;top:100%;left:0;right:0;background:#0b1220;flex-direction:column;padding:8px 18px;gap:2px;border-bottom:1px solid #1e293b}
  .nav-links.open{display:flex}
  .nav-links a{padding:10px 12px;font-size:14px;color:#f8fafc}
}