/* Sticky header */
.site-header{
  position: sticky;
  top: 0;
  z-index: 1000;
  backdrop-filter: blur(12px);
  background: rgba(255,255,255,.85);
  border-bottom: 1px solid rgba(0,0,0,.06);
  transition: background .2s ease, box-shadow .2s ease;
}

html[data-theme="dark"] .site-header{
  background: rgba(15,23,42,.82);
  border-bottom: 1px solid rgba(255,255,255,.08);
}

.site-header.scrolled{
  box-shadow: 0 10px 30px rgba(0,0,0,.08);
}

.header-inner{
  display:flex;
  align-items:center;
  justify-content:space-between;
  height:72px;
  gap:1rem;
}

/* Brand */
.brand{
  text-decoration:none;
  font-weight:900;
  font-size:1.05rem;
  letter-spacing:-0.02em;
  color:var(--text);
}

/* Nav */
.main-nav{
  display:flex;
  gap:.4rem;
}

.nav-link{
  position:relative;
  padding:.55rem .9rem;
  border-radius:999px;
  font-weight:700;
  font-size:.92rem;
  text-decoration:none;
  color:var(--text-muted);
  transition:.18s ease;
}

.nav-link:hover{
  transform:translateY(-2px);
  background:rgba(37,99,235,.12);
  color:var(--text);
}

/* Underline animation */
.nav-link::after{
  content:"";
  position:absolute;
  left:16px;
  right:16px;
  bottom:8px;
  height:2px;
  background:var(--accent,#2563eb);
  border-radius:2px;
  opacity:0;
  transform:translateY(4px) scaleX(.6);
  transition:.18s ease;
}

.nav-link:hover::after{
  opacity:1;
  transform:translateY(0) scaleX(1);
}

.nav-link.active{
  background:rgba(37,99,235,.18);
  color:var(--text);
}

.nav-link.active::after{
  opacity:1;
  transform:translateY(0) scaleX(1);
}

/* Actions */
.header-actions{
  display:flex;
  align-items:center;
  gap:.6rem;
}

/* Social */
.social-links{
  display:flex;
  gap:.3rem;
}

.icon-link{
  width:36px;
  height:36px;
  display:flex;
  align-items:center;
  justify-content:center;
  border-radius:10px;
  color:var(--text-muted);
  text-decoration:none;
  transition:.18s ease;
}

.icon-link:hover{
  transform:translateY(-2px) scale(1.05);
  background:rgba(37,99,235,.15);
  color:var(--text);
}

/* Theme toggle icons */
.theme-toggle{
  position:relative;
}

.theme-toggle i{
  position:absolute;
  transition:.2s ease;
}

.icon-moon{ opacity:1; transform:rotate(0); }
.icon-sun{ opacity:0; transform:rotate(90deg) scale(.8); }

html[data-theme="dark"] .icon-moon{
  opacity:0;
  transform:rotate(-90deg) scale(.8);
}

html[data-theme="dark"] .icon-sun{
  opacity:1;
  transform:rotate(0);
}

/* Responsive */
@media (max-width: 950px){
  .main-nav{ display:none; }
}