/* ==========================================
   Header / Navigation
   ========================================== */
.site-header {
  position: sticky;
  top: 0;
  z-index: 100;
  background: #fff;
  border-bottom: 1px solid var(--color-border-light);
  backdrop-filter: saturate(180%) blur(10px);
  background: rgba(255, 255, 255, 0.95);
}
.site-header__inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: var(--header-height);
}
.site-header__brand { display: flex; align-items: center; }
.site-header__logo {
  display: flex;
  align-items: center;
  gap: var(--space-sm);
  font-weight: 900;
  color: var(--color-text);
  text-decoration: none;
}
.site-header__logo-mark {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 40px;
  height: 40px;
  border-radius: 50%;
  background: var(--color-primary);
  color: #fff;
  font-size: 22px;
  font-weight: 900;
}
.site-header__logo-text {
  font-size: 18px;
  letter-spacing: 0.02em;
}
.site-header__nav { display: flex; }
.site-nav {
  display: flex;
  list-style: none;
  margin: 0;
  padding: 0;
  gap: var(--space-lg);
}
.site-nav li { margin: 0; }
.site-nav a {
  display: inline-block;
  padding: var(--space-sm) var(--space-md);
  color: var(--color-text);
  font-weight: 500;
  font-size: 15px;
  transition: color var(--transition-fast);
}
.site-nav a:hover { color: var(--color-primary); text-decoration: none; }
.site-nav__cta,
.site-nav a.site-nav__cta {
  background: var(--color-primary);
  color: #fff;
  border-radius: var(--radius-md);
  padding: 0.5em 1.2em;
}
.site-nav__cta:hover,
.site-nav a.site-nav__cta:hover {
  background: var(--color-primary-dark);
  color: #fff;
}

.site-header__menu-toggle {
  display: none;
  flex-direction: column;
  gap: 5px;
  background: none;
  border: 0;
  width: 32px;
  height: 32px;
  cursor: pointer;
  padding: 0;
  justify-content: center;
  align-items: center;
}
.site-header__menu-toggle span {
  display: block;
  width: 24px;
  height: 2px;
  background: var(--color-text);
  transition: var(--transition-base);
}
.site-header__menu-toggle[aria-expanded="true"] span:nth-child(1) { transform: translateY(7px) rotate(45deg); }
.site-header__menu-toggle[aria-expanded="true"] span:nth-child(2) { opacity: 0; }
.site-header__menu-toggle[aria-expanded="true"] span:nth-child(3) { transform: translateY(-7px) rotate(-45deg); }

@media (max-width: 768px) {
  .site-header__menu-toggle { display: flex; }
  .site-header__nav {
    position: fixed;
    top: var(--header-height);
    left: 0;
    right: 0;
    background: #fff;
    border-top: 1px solid var(--color-border-light);
    transform: translateY(-100%);
    opacity: 0;
    pointer-events: none;
    transition: var(--transition-base);
  }
  .site-header__nav.is-open {
    transform: translateY(0);
    opacity: 1;
    pointer-events: auto;
  }
  .site-nav {
    flex-direction: column;
    padding: var(--space-md);
    gap: 0;
  }
  .site-nav a { display: block; padding: var(--space-md); border-bottom: 1px solid var(--color-border-light); }
}

/* スキップリンク */
.skip-link {
  position: absolute;
  left: -9999px;
  top: 0;
  background: #000;
  color: #fff;
  padding: 8px 16px;
  z-index: 9999;
}
.skip-link:focus { left: 8px; top: 8px; }