/* ═══════════════════════════════════════════════
   头部导航 + 主题切换按钮
   ═══════════════════════════════════════════════ */

.site-header {
  position: sticky;
  top: 0;
  z-index: 100;
  background: var(--color-canvas);
  border-bottom: 1px solid var(--color-hairline);
}

.site-header .container {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding-top: var(--spacing-lg);
  padding-bottom: var(--spacing-lg);
}

/* ── 站点标题 ── */
.site-title {
  font-family: var(--font-display);
  font-size: var(--text-h3);
  font-weight: var(--weight-normal);
  color: var(--color-ink);
  text-decoration: none;
  flex-shrink: 0;
}

.site-title:hover {
  text-decoration: none;
  color: var(--color-primary);
}

/* ── 导航菜单 ── */
.site-nav {
  display: flex;
  gap: var(--spacing-lg);
  list-style: none;
  margin: 0;
  padding: 0;
}

.site-nav a {
  font-size: var(--text-caption);
  font-weight: var(--weight-medium);
  color: var(--color-muted);
  text-transform: uppercase;
  letter-spacing: 0.5px;
}

.site-nav a:hover {
  color: var(--color-primary);
  text-decoration: none;
}

/* ── 主题切换按钮 ── */
/* 36px 圆形，发丝边框，悬停变珊瑚色 */
.theme-toggle {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 36px;
  height: 36px;
  padding: 0;
  background: none;
  border: 1px solid var(--color-hairline);
  border-radius: 50%;
  cursor: pointer;
  color: var(--color-muted);
  font-size: 16px;
  line-height: 1;
  transition: border-color 0.15s, color 0.15s;
  flex-shrink: 0;
}

.theme-toggle:hover {
  color: var(--color-primary);
  border-color: var(--color-primary);
}

/* 浅色模式：显示月亮图标（☾）→ 点击切换到深色 */
html[data-theme="light"] .theme-toggle-light { display: inline; }
html[data-theme="light"] .theme-toggle-dark  { display: none; }

/* 深色模式：显示太阳图标（☀）→ 点击切换到浅色 */
html[data-theme="dark"] .theme-toggle-light { display: none; }
html[data-theme="dark"] .theme-toggle-dark  { display: inline; }

/* ═══════════════════════════════════════════════
   响应式
   ═══════════════════════════════════════════════ */

/* 移动端：减小头部内边距，标题缩小，导航间距收窄 */
@media (max-width: 768px) {
  .site-header .container {
    padding-top: var(--spacing-md);
    padding-bottom: var(--spacing-md);
  }

  .site-title {
    font-size: 20px;
  }

  .site-nav {
    gap: var(--spacing-md);
  }

  .site-nav a {
    font-size: 12px;
    letter-spacing: 0;
  }

  .theme-toggle {
    width: 32px;
    height: 32px;
    font-size: 14px;
  }
}