.site-header{
  position: fixed;
  inset: 0 0 auto 0;
  z-index: 100;
  height: var(--header-h);
  display: flex;
  align-items: center;
  background: transparent;
  transition: background var(--dur-med) var(--ease-out), box-shadow var(--dur-med), backdrop-filter var(--dur-med);
}
.site-header::before{
  content: '';
  position: absolute;
  inset: 0 0 auto 0;
  height: 220%;
  background: linear-gradient(to bottom, rgba(0,0,0,0.5), rgba(0,0,0,0));
  z-index: -1;
  opacity: 0;
  transition: opacity var(--dur-med) var(--ease-out);
  pointer-events: none;
}
.site-header.header-on-dark::before{ opacity: 1; }
.site-header.is-scrolled{
  background: rgba(var(--color-bg-rgb), 0.82);
  backdrop-filter: blur(14px) saturate(1.2);
  -webkit-backdrop-filter: blur(14px) saturate(1.2);
  box-shadow: 0 1px 0 var(--color-line);
}
.site-header .container{
  display: flex;
  align-items: center;
  justify-content: space-between;
  width: 100%;
  gap: 1.5rem;
}

.logo{
  font-family: var(--font-display);
  font-weight: 900;
  font-size: clamp(36px, 2.8vw, 56px);
  letter-spacing: -0.02em;
  color: var(--color-black);
  transition: color var(--dur-fast);
}
.header-on-dark .logo{ color: var(--color-white); }
.logo .accent-dot{ color: var(--hero-accent); }

.btn-accent{
  background: var(--hero-accent);
  color: var(--hero-black);
}
.btn-accent:hover{ background: var(--hero-black); color: var(--hero-accent); }

.main-nav{
  display: flex;
  align-items: center;
  gap: clamp(1.2rem, 2.4vw, 2.6rem);
}
.main-nav a{
  font-family: var(--font-display);
  font-weight: 600;
  font-size: 0.95rem;
  color: var(--color-black);
  position: relative;
  padding-block: 0.3rem;
  transition: color var(--dur-fast);
}
.header-on-dark .main-nav a{ color: var(--color-white); }
.main-nav a::after{
  content: '';
  position: absolute;
  right: 0; left: 0; bottom: -2px;
  height: 2px;
  background: var(--hero-accent);
  transform: scaleX(0);
  transform-origin: right;
  transition: transform var(--dur-fast) var(--ease-out);
}
.main-nav a:hover::after,
.main-nav a:focus-visible::after{ transform: scaleX(1); }

.header-actions{
  display: flex;
  align-items: center;
  gap: 1.4rem;
}
.login-link{
  font-family: var(--font-display);
  font-weight: 600;
  font-size: 0.9rem;
  color: var(--color-black);
}
.header-on-dark .login-link{ color: var(--color-white); }

.header-actions .btn{ padding: 0.75rem 1.3rem; font-size: 0.85rem; }

.nav-toggle{
  display: none;
  flex-direction: column;
  gap: 5px;
  width: 34px;
  height: 34px;
  align-items: center;
  justify-content: center;
}
.nav-toggle span{
  width: 22px; height: 2px;
  background: var(--color-black);
  transition: transform var(--dur-fast), opacity var(--dur-fast);
}
.header-on-dark .nav-toggle span{ background: var(--color-white); }
.site-header.is-scrolled .nav-toggle span{ background: var(--color-black); }

@media (max-width: 900px){
  .main-nav{ display: none; }
  .login-link{ display: none; }
  .nav-toggle{ display: flex; }
}

/* Mobile menu overlay */
.mobile-nav{
  position: fixed;
  inset: 0;
  z-index: 99;
  background: var(--color-black);
  color: var(--color-white);
  display: flex;
  flex-direction: column;
  justify-content: center;
  gap: 2rem;
  padding: var(--gutter);
  transform: translateY(-100%);
  transition: transform var(--dur-med) var(--ease-editorial);
}
.mobile-nav.is-open{ transform: translateY(0); }
.mobile-nav a{
  font-family: var(--font-display);
  font-weight: 800;
  font-size: 2rem;
  letter-spacing: -0.02em;
}
.mobile-nav .header-actions{ margin-top: 1.5rem; flex-direction: column; align-items: flex-start; gap: 1rem; }
.mobile-nav .login-link{ display: inline-block; color: var(--color-white); font-size: 1.1rem; }