.site-header {
  position: fixed;
  z-index: 2;
  top: clamp(1rem, 2.4vw, 2rem);
  left: 50%;
  transform: translateX(-50%);
  display: grid;
  grid-template-columns: minmax(8.5rem, 11rem) 1fr auto;
  align-items: center;
  gap: clamp(1rem, 3vw, 3rem);
  width: min(calc(100% - 2rem), 76rem);
  min-height: 4.6rem;
  padding: .7rem .85rem .7rem 1.1rem;
  border: 1px solid var(--color-border);
  border-radius: 1.35rem;
  background: var(--color-surface);
  box-shadow: 0 0 2.5rem rgba(6, 103, 213, 0.1), inset 0 1px rgba(255,255,255,.08);
  backdrop-filter: blur(1rem);
}

.site-header__brand { display: inline-flex; min-width: 0; }
.site-header__brand img { width: min(100%, 10.4rem); height: auto; }
:root[data-theme='light'] .site-header__brand { padding: .28rem .45rem; border-radius: .6rem; background: linear-gradient(135deg, #071b38, #0a3266); box-shadow: 0 .2rem .7rem rgba(15, 76, 145, .16); }
.site-header__nav { display: flex; justify-content: center; gap: clamp(1rem, 2.4vw, 2.25rem); }
.site-header__nav a { color: var(--color-text-muted); font: 500 .9rem/1 system-ui, sans-serif; text-decoration: none; transition: color .2s ease, text-shadow .2s ease; }
.site-header__nav a:hover { color: var(--color-text); text-shadow: 0 0 .8rem rgba(49, 145, 255, .55); }
.site-header__actions { display: flex; align-items: center; gap: .65rem; }
.theme-toggle, .menu-toggle, .site-header__cta { border: 0; font: inherit; cursor: pointer; }
.theme-toggle, .menu-toggle { display: grid; place-items: center; width: 2.45rem; height: 2.45rem; border: 1px solid var(--color-border); border-radius: .8rem; color: var(--color-text); background: color-mix(in srgb, var(--color-surface) 85%, transparent); }
.theme-toggle svg { position: absolute; width: 1.12rem; fill: none; stroke: currentColor; stroke-width: 1.7; stroke-linecap: round; }
.theme-toggle__sun { opacity: 0; transform: rotate(-50deg) scale(.65); }
.theme-toggle__moon { opacity: 1; }
:root[data-theme='light'] .theme-toggle__sun { opacity: 1; transform: rotate(0) scale(1); }
:root[data-theme='light'] .theme-toggle__moon { opacity: 0; transform: rotate(50deg) scale(.65); }
.theme-toggle svg { transition: opacity .2s ease, transform .25s ease; }
.site-header__cta { padding: .72rem 1rem; border-radius: .8rem; color: #fff; background: linear-gradient(135deg, var(--color-accent), var(--color-accent-strong)); box-shadow: 0 .4rem 1rem rgba(3, 93, 192, .28); font-size: .84rem; font-weight: 650; transition: transform .2s ease, box-shadow .2s ease; }
.site-header__cta:hover { transform: translateY(-1px); box-shadow: 0 .55rem 1.2rem rgba(3, 93, 192, .4); }
.menu-toggle { display: none; padding: .55rem; gap: .22rem; }
.menu-toggle span { display: block; width: 1.1rem; height: 1px; background: currentColor; }
.theme-toggle:focus-visible, .menu-toggle:focus-visible, .site-header__cta:focus-visible, .site-header__nav a:focus-visible, .site-header__brand:focus-visible { outline: 2px solid var(--color-focus); outline-offset: 3px; }

@media (max-width: 52rem) {
  .site-header { grid-template-columns: 1fr auto; gap: .75rem; }
  .site-header__nav { position: absolute; top: calc(100% + .6rem); right: 0; left: 0; display: none; flex-direction: column; align-items: stretch; gap: .2rem; padding: .6rem; border: 1px solid var(--color-border); border-radius: 1rem; background: var(--color-surface); backdrop-filter: blur(1rem); }
  .site-header__nav.is-open { display: flex; }
  .site-header__nav a { padding: .8rem .9rem; border-radius: .65rem; }
  .site-header__nav a:hover { background: color-mix(in srgb, var(--color-accent) 10%, transparent); }
  .menu-toggle { display: grid; }
}

@media (max-width: 28rem) { .site-header__cta { display: none; } }
@media (prefers-reduced-motion: reduce) { .site-header *, .theme-toggle svg { transition: none; } }