.site-header{position:sticky;top:0;z-index:1000;background:var(--color-bg-surface);border-bottom:1px solid var(--color-border)}
.header-inner{display:flex;align-items:center;justify-content:space-between;min-height:72px}
.brand-link{display:flex;align-items:center;gap:12px}
.brand-mark{height:52px;width:auto}
.brand-text{font-family:var(--font-heading);font-size:1.5rem}
.primary-nav{display:flex}
.nav-list{display:flex;gap:24px}
.nav-list a{position:relative}
.nav-list a::after{content:"";position:absolute;left:0;bottom:-4px;width:0;height:1px;background:var(--color-accent);transition:width var(--transition-fast)}
.nav-list a:hover::after{width:100%}
.nav-toggle-btn{display:none;width:40px;height:40px;align-items:center;justify-content:center}
.nav-toggle-btn span{display:block;width:20px;height:2px;background:#fff}
@media (max-width:900px){
  .brand-mark{height:40px}
  .brand-text{font-size:1.1rem}
  .nav-toggle-btn{display:flex;flex-direction:column;gap:4px}
  .primary-nav{position:fixed;top:72px;left:0;width:100%;background:var(--color-bg-surface);max-height:calc(100vh - 72px);overflow:auto;transform:translateY(-120%);transition:transform var(--transition-fast)}
  .primary-nav.open{transform:translateY(0)}
  .nav-list{flex-direction:column;padding:16px}
}