/* ============================================
   layout.css — 头部、导航、页脚、主布局
   ============================================ */

/* ---------- 头部 ---------- */
.site-header {
  border-bottom: 1px solid var(--border);
  background-color: var(--bg);
  position: sticky;
  top: 0;
  z-index: 100;
  backdrop-filter: blur(8px);
  -webkit-backdrop-filter: blur(8px);
  background-color: color-mix(in srgb, var(--bg) 85%, transparent);
}

.site-header__inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 18px 0;
  gap: 24px;
}

.brand {
  display: flex;
  flex-direction: column;
  gap: 2px;
  border-bottom: none;
}

.brand__title {
  font-family: var(--font-serif);
  font-size: 1.375rem;
  font-weight: 700;
  letter-spacing: 0.02em;
  color: var(--text);
  line-height: 1.2;
}

.brand__subtitle {
  font-family: var(--font-sans);
  font-size: 0.75rem;
  color: var(--text-muted);
  letter-spacing: 0.05em;
}

/* ---------- 导航 ---------- */
.nav {
  display: flex;
  align-items: center;
  gap: 28px;
}

.nav__link {
  font-family: var(--font-sans);
  font-size: 0.9375rem;
  color: var(--text-muted);
  border-bottom: 1px solid transparent;
  padding-bottom: 2px;
  transition: color 0.2s, border-color 0.2s;
}

.nav__link:hover,
.nav__link.is-active {
  color: var(--text);
  border-bottom-color: var(--accent);
}

.nav__theme {
  width: 36px;
  height: 36px;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  border: 1px solid var(--border);
  border-radius: 50%;
  color: var(--text-muted);
  transition: all 0.2s;
}

.nav__theme:hover {
  color: var(--accent);
  border-color: var(--accent);
}

.nav__theme svg {
  width: 16px;
  height: 16px;
}

/* ---------- 页脚 ---------- */
.site-footer {
  border-top: 1px solid var(--border);
  margin-top: 96px;
  padding: 48px 0;
  font-family: var(--font-sans);
  font-size: 0.875rem;
  color: var(--text-muted);
}

.site-footer__inner {
  display: flex;
  flex-direction: column;
  gap: 16px;
  align-items: center;
  text-align: center;
}

.site-footer__social {
  display: flex;
  gap: 20px;
  margin-bottom: 8px;
}

.site-footer__social a {
  border-bottom: none;
  color: var(--text-muted);
}

.site-footer__social a:hover {
  color: var(--accent);
}

.site-footer__copy {
  letter-spacing: 0.02em;
}

.site-footer__copy a {
  border-bottom: none;
  color: var(--text-muted);
}

.site-footer__copy a:hover {
  color: var(--accent);
}

/* ---------- 主区域 ---------- */
.main {
  padding: 48px 0 64px;
}

/* 页面标题区 */
.page-header {
  text-align: center;
  margin-bottom: 64px;
  padding: 32px 0;
  border-bottom: 1px solid var(--border);
}

.page-header__eyebrow {
  font-family: var(--font-sans);
  font-size: 0.75rem;
  letter-spacing: 0.2em;
  text-transform: uppercase;
  color: var(--accent);
  margin-bottom: 16px;
}

.page-header__title {
  font-family: var(--font-serif);
  font-size: 2.5rem;
  font-weight: 700;
  line-height: 1.2;
  margin-bottom: 12px;
  letter-spacing: -0.01em;
}

.page-header__subtitle {
  font-family: var(--font-serif);
  font-size: 1.125rem;
  color: var(--text-muted);
  font-style: italic;
  max-width: 540px;
  margin: 0 auto;
}

/* ---------- 响应式 ---------- */
@media (max-width: 720px) {
  .site-header__inner {
    flex-wrap: wrap;
    gap: 12px;
  }

  .nav {
    gap: 18px;
    flex-wrap: wrap;
  }

  .nav__link {
    font-size: 0.875rem;
  }

  .page-header__title {
    font-size: 2rem;
  }

  .main {
    padding: 32px 0 48px;
  }
}