.site-header {
  position: fixed;
  top: 0; left: 0; right: 0;
  height: var(--header-h);
  background: rgba(255,255,255,.92);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--color-border);
  z-index: 100;
}
.site-header__inner {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 var(--space-lg);
  height: 100%;
  display: flex;
  align-items: center;
  gap: var(--space-xl);
}

/* Logo */
.site-logo {
  display: flex;
  align-items: center;
  gap: 0;
  flex-shrink: 0;
  text-decoration: none;
}
.logo-icon {
  width: 36px; height: 36px;
  background: var(--color-primary);
  border-radius: 9px;
  display: flex; align-items: center; justify-content: center;
  color: #fff;
  font-family: var(--font-heading);
  font-weight: 800;
  font-size: 1.1rem;
  letter-spacing: -.02em;
  flex-shrink: 0;
}
.logo-wordmark {
  font-family: var(--font-heading);
  font-weight: 800;
  font-size: 1.35rem;
  letter-spacing: -1.2px;
  color: var(--color-dark);
  padding-left: 2px;
}

/* Nav links */
.nav-links {
  display: flex;
  align-items: center;
  gap: var(--space-xs);
  flex: 1;
  justify-content: center;
}
.nav-link {
  font-size: .875rem;
  font-weight: 500;
  color: var(--color-muted);
  padding: 6px 12px;
  border-radius: var(--radius-full);
  transition: color var(--dur), background var(--dur);
  white-space: nowrap;
}
.nav-link:hover { color: var(--color-primary); background: #EEF2FF; }

/* Right side */
.site-header__right {
  display: flex;
  align-items: center;
  gap: var(--space-md);
  flex-shrink: 0;
  margin-left: auto;
}

/* Desktop search */
.nav-search {
  position: relative;
  display: flex;
  align-items: center;
}
.nav-search__icon {
  position: absolute;
  left: 12px;
  color: var(--color-muted);
  pointer-events: none;
}
.nav-search__input {
  height: 36px;
  width: 200px;
  padding: 0 var(--space-md) 0 36px;
  border: 1.5px solid var(--color-border);
  border-radius: var(--radius-full);
  font-family: var(--font-body);
  font-size: .875rem;
  color: var(--color-dark);
  background: var(--color-bg);
  transition: border-color var(--dur), width var(--dur) var(--ease), box-shadow var(--dur);
  outline: none;
}
.nav-search__input::placeholder { color: var(--color-muted); }
.nav-search__input:focus {
  border-color: var(--color-primary);
  width: 260px;
  box-shadow: 0 0 0 3px rgba(79,70,229,.1);
  background: var(--color-white);
}

/* Burger */
.nav-burger {
  display: none;
  flex-direction: column;
  gap: 5px;
  padding: 6px;
  border-radius: var(--radius-sm);
  transition: background var(--dur);
}
.nav-burger:hover { background: var(--color-bg); }
.nav-burger span {
  display: block;
  width: 20px; height: 2px;
  background: var(--color-dark);
  border-radius: 2px;
  transition: transform var(--dur) var(--ease), opacity var(--dur);
}
.nav-burger.open span:nth-child(1) { transform: translateY(7px) rotate(45deg); }
.nav-burger.open span:nth-child(2) { opacity: 0; }
.nav-burger.open span:nth-child(3) { transform: translateY(-7px) rotate(-45deg); }

/* Mobile menu */
.nav-mobile {
  display: none;
  position: fixed;
  top: var(--header-h);
  left: 0; right: 0;
  background: var(--color-white);
  border-bottom: 1px solid var(--color-border);
  z-index: 99;
  padding: var(--space-md) var(--space-lg) var(--space-lg);
  box-shadow: var(--shadow-lg);
  max-height: calc(100vh - var(--header-h));
  overflow-y: auto;
}
.nav-mobile.is-open { display: block; }

.mob-search {
  position: relative;
  display: flex;
  align-items: center;
  margin-bottom: var(--space-md);
}
.mob-search svg {
  position: absolute;
  left: 12px;
  color: var(--color-muted);
}
.mob-search input {
  width: 100%;
  height: 40px;
  padding: 0 var(--space-md) 0 36px;
  border: 1.5px solid var(--color-border);
  border-radius: var(--radius-full);
  font-family: var(--font-body);
  font-size: .9rem;
  outline: none;
}
.mob-search input:focus { border-color: var(--color-primary); }

.mob-divider { height: 1px; background: var(--color-border); margin: var(--space-sm) 0; }
.mob-section-label {
  font-size: .72rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: .08em;
  color: var(--color-muted);
  padding: var(--space-sm) 0 var(--space-xs);
}
.mob-link {
  display: flex;
  align-items: center;
  gap: var(--space-md);
  padding: 10px var(--space-sm);
  border-radius: var(--radius-sm);
  font-size: .9rem;
  font-weight: 500;
  color: var(--color-text);
  transition: background var(--dur), color var(--dur);
}
.mob-link:hover { background: var(--color-bg); color: var(--color-primary); }
.mob-icon {
  width: 32px; height: 32px;
  border-radius: var(--radius-sm);
  background: var(--color-bg);
  display: flex; align-items: center; justify-content: center;
  flex-shrink: 0;
  color: var(--color-muted);
}
.mob-icon--calculators { background: var(--cat-calc-bg); color: var(--cat-calc-icon); }
.mob-icon--ai          { background: var(--cat-ai-bg);   color: var(--cat-ai-icon); }
.mob-icon--pdf         { background: var(--cat-pdf-bg);  color: var(--cat-pdf-icon); }
.mob-icon--file        { background: var(--cat-file-bg); color: var(--cat-file-icon); }
.mob-icon--converters  { background: var(--cat-conv-bg); color: var(--cat-conv-icon); }

/* Responsive */
@media (max-width: 900px) {
  .nav-links { display: none; }
  .nav-burger { display: flex; }
  .nav-search__input { width: 160px; }
  .nav-search__input:focus { width: 200px; }
}
@media (max-width: 480px) {
  .site-header__right { flex: 1; }
  .nav-search { flex: 1; }
  .nav-search__input { width: 100%; }
  .nav-search__input:focus { width: 100%; }
}