.site-header {
  position: sticky;
  top: 0;
  z-index: 100;
  height: var(--header-h);
  background: rgba(255, 255, 255, 0.9);
  backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--border);
}

.header-inner {
  height: 100%;
  width: 100%;
  padding-inline: clamp(24px, 3.5vw, 64px);
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1.5rem;
}

.brand-logo { height: 30px; width: auto; }

.nav { display: flex; align-items: center; gap: 2.2rem; }
.nav a {
  font-size: 0.98rem;
  font-weight: 600;
  color: var(--text);
  position: relative;
  padding-block: 4px;
  transition: color 0.18s ease;
}
.nav a::after {
  content: "";
  position: absolute;
  left: 0; bottom: 0;
  width: 0; height: 2px;
  background: var(--brand);
  transition: width 0.22s ease;
}
.nav a:hover { color: var(--brand); }
.nav a:hover::after { width: 100%; }

/* Nút menu mobile — ẩn ở desktop, bật ở phase responsive */
.nav-toggle {
  display: none;
  flex-direction: column;
  justify-content: center;
  gap: 5px;
  width: 42px;
  height: 42px;
  background: transparent;
  border: none;
  cursor: pointer;
}
.nav-toggle span {
  display: block;
  width: 24px;
  height: 2px;
  background: var(--text);
  border-radius: 2px;
  transition: transform 0.25s ease, opacity 0.25s ease;
}