/* ============================================================
   Navigation — Header, links, mobile toggle
   ============================================================ */

.site-header {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 100;
  padding: 0.75rem 0;
  transition: background var(--md-motion-duration-medium) var(--md-motion-easing-standard),
              box-shadow var(--md-motion-duration-medium) var(--md-motion-easing-standard);
}

.site-header.scrolled {
  background: rgba(15, 20, 22, 0.85);
  backdrop-filter: blur(16px);
  -webkit-backdrop-filter: blur(16px);
  box-shadow: var(--md-elevation-2);
}

.nav {
  display: flex;
  align-items: center;
  justify-content: space-between;
  max-width: 1200px;
  margin-inline: auto;
  padding-inline: clamp(1rem, 5vw, 4rem);
}

.nav-logo {
  display: flex;
  align-items: center;
  gap: 0.625rem;
  color: var(--md-sys-color-primary);
  transition: opacity var(--md-motion-duration-short) var(--md-motion-easing-standard);
}

.nav-logo:hover {
  opacity: 0.8;
}

.nav-logo svg,
.nav-logo img {
  width: 36px;
  height: 36px;
}

.nav-logo-text {
  font-family: var(--md-sys-typescale-display-font);
  font-weight: 600;
  font-size: 1.125rem;
  letter-spacing: 0.02em;
}

.nav-links {
  display: flex;
  align-items: center;
  gap: 0.25rem;
}

.nav-link {
  position: relative;
  padding: 0.5rem 1rem;
  font-family: var(--md-sys-typescale-body-font);
  font-weight: var(--md-sys-typescale-label-weight);
  font-size: var(--md-sys-typescale-label-size);
  color: var(--md-sys-color-on-surface-variant);
  border-radius: var(--md-sys-shape-sm);
  transition: color var(--md-motion-duration-short) var(--md-motion-easing-standard),
              background var(--md-motion-duration-short) var(--md-motion-easing-standard);
  overflow: hidden;
}

.nav-link:hover {
  color: var(--md-sys-color-primary);
  background: rgba(134, 210, 230, 0.08);
}

.nav-link.active {
  color: var(--md-sys-color-primary);
}

.nav-toggle {
  display: none;
  flex-direction: column;
  gap: 5px;
  background: none;
  border: none;
  cursor: pointer;
  padding: 8px;
  min-width: 48px;
  min-height: 48px;
  align-items: center;
  justify-content: center;
}

.nav-toggle span {
  display: block;
  width: 24px;
  height: 2px;
  background: var(--md-sys-color-on-surface);
  border-radius: var(--md-sys-shape-full);
  transition: transform var(--md-motion-duration-medium) var(--md-motion-easing-standard),
              opacity var(--md-motion-duration-short) var(--md-motion-easing-standard);
}

.nav-toggle.active span:nth-child(1) {
  transform: translateY(7px) rotate(45deg);
}

.nav-toggle.active span:nth-child(2) {
  opacity: 0;
}

.nav-toggle.active span:nth-child(3) {
  transform: translateY(-7px) rotate(-45deg);
}