/* ヘッダー・サイドバー・フッター・全体グリッド */

.site-header {
  position: sticky; top: 0; z-index: 100;
  background: color-mix(in srgb, var(--color-bg-elevated) 88%, transparent);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--color-border);
  height: var(--header-height);
}
.site-header__inner {
  max-width: 1400px; margin: 0 auto; height: 100%;
  display: flex; align-items: center; gap: var(--space-6);
  padding: 0 var(--space-5);
}
.site-logo {
  display: flex; align-items: center; gap: var(--space-2);
  font-weight: 700; font-size: 1.05rem; color: var(--color-text);
  text-decoration: none; flex-shrink: 0;
}
.site-logo__domain { color: var(--color-text-secondary); font-weight: 400; }
.site-logo__image { height: 34px; width: auto; }

.nav-toggle {
  display: none; margin-left: auto; background: none; border: none; cursor: pointer;
  width: 40px; height: 40px; border-radius: var(--radius-sm); flex-direction: column;
  align-items: center; justify-content: center; gap: 5px;
}
.nav-toggle__bar { width: 20px; height: 2px; background: var(--color-text); border-radius: 2px; }

.site-nav { display: flex; align-items: center; gap: var(--space-2); margin-left: auto; flex-wrap: wrap; }
.site-nav a {
  color: var(--color-text-secondary); text-decoration: none; font-weight: 600; font-size: 0.88rem;
  padding: var(--space-2) var(--space-3); border-radius: var(--radius-sm);
  transition: background var(--transition-fast), color var(--transition-fast);
  white-space: nowrap;
}
.site-nav a:hover { background: var(--color-bg-subtle); color: var(--color-text); }
.site-nav a.is-active { background: var(--color-bg-brand-subtle); color: var(--color-brand); }

.page-shell {
  max-width: 1400px; margin: 0 auto;
  display: grid; grid-template-columns: var(--sidebar-width) minmax(0, 1fr);
  gap: var(--space-8); align-items: start;
  padding: var(--space-6) var(--space-5) var(--space-12);
}

.sidebar {
  position: sticky; top: calc(var(--header-height) + var(--space-6));
  max-height: calc(100vh - var(--header-height) - var(--space-10));
  overflow-y: auto; padding-right: var(--space-2);
}
.sidebar-nav { display: flex; flex-direction: column; gap: var(--space-1); font-size: 0.93rem; }
.sidebar-subject { border-radius: var(--radius-md); }
.sidebar-subject > summary {
  cursor: pointer; list-style: none; padding: var(--space-2) var(--space-3);
  border-radius: var(--radius-md); font-weight: 700; display: flex; align-items: center;
}
.sidebar-subject > summary::-webkit-details-marker { display: none; }
.sidebar-subject > summary::before {
  content: "›"; display: inline-block; margin-right: var(--space-2);
  transition: transform var(--transition-fast); font-weight: 700; color: var(--color-text-tertiary);
}
.sidebar-subject[open] > summary::before { transform: rotate(90deg); }
.sidebar-subject > summary a { color: inherit; text-decoration: none; flex: 1; }
.sidebar-subject > summary:hover { background: var(--color-bg-subtle); }
.grade-tag { font-size: 0.72rem; font-weight: 400; color: var(--color-text-tertiary); }

.sidebar-unit { margin: 0 0 var(--space-1) var(--space-5); }
.sidebar-unit > summary {
  cursor: pointer; list-style: none; padding: var(--space-1) var(--space-2);
  border-radius: var(--radius-sm); font-weight: 600; color: var(--color-text-secondary);
  display: flex; align-items: center; font-size: 0.9rem;
}
.sidebar-unit > summary::-webkit-details-marker { display: none; }
.sidebar-unit > summary::before {
  content: "›"; display: inline-block; margin-right: var(--space-2);
  transition: transform var(--transition-fast); color: var(--color-text-tertiary);
}
.sidebar-unit[open] > summary::before { transform: rotate(90deg); }
.sidebar-unit > summary a { color: inherit; text-decoration: none; flex: 1; }
.sidebar-unit > summary:hover { background: var(--color-bg-subtle); }
.sidebar-unit ul { list-style: none; margin: 0; padding-left: var(--space-6); }
.sidebar-unit li { margin: 0; }
.sidebar-unit a {
  display: block; padding: var(--space-1) var(--space-2); border-radius: var(--radius-sm);
  color: var(--color-text-secondary); text-decoration: none; font-size: 0.87rem;
}
.sidebar-unit a:hover { background: var(--color-bg-subtle); color: var(--color-text); }
.sidebar-unit a.is-current { background: var(--color-bg-brand-subtle); color: var(--color-brand); font-weight: 700; }
.sidebar-unit a.sidebar-extra { color: var(--color-text-tertiary); }

.sidebar-toplink {
  display: block; margin-top: var(--space-3); padding: var(--space-2) var(--space-3);
  border-radius: var(--radius-md); text-decoration: none; font-weight: 700;
  color: var(--color-text-secondary); border: 1px solid var(--color-border);
}
.sidebar-toplink:hover { background: var(--color-bg-subtle); }

.content { min-width: 0; }

.site-footer { border-top: 1px solid var(--color-border); margin-top: var(--space-12); background: var(--color-bg-subtle); }
.site-footer__inner {
  max-width: 1400px; margin: 0 auto; padding: var(--space-10) var(--space-5) var(--space-6);
  display: flex; flex-wrap: wrap; gap: var(--space-8); justify-content: space-between;
}
.site-footer__title { font-weight: 700; margin: 0 0 var(--space-2); }
.site-footer__desc { color: var(--color-text-secondary); max-width: 420px; margin: 0; font-size: 0.92rem; }
.site-footer__links { display: flex; flex-direction: column; gap: var(--space-2); font-size: 0.92rem; }
.site-footer__links a { color: var(--color-text-secondary); text-decoration: none; }
.site-footer__links a:hover { color: var(--color-brand); }
.site-footer__copy { text-align: center; color: var(--color-text-tertiary); font-size: 0.82rem; padding: var(--space-4) 0; margin: 0; }

@media (max-width: 960px) {
  .page-shell { grid-template-columns: 1fr; }
  .nav-toggle { display: flex; }
  .site-nav {
    display: none; position: absolute; top: var(--header-height); left: 0; right: 0;
    background: var(--color-bg-elevated); border-bottom: 1px solid var(--color-border);
    flex-direction: column; align-items: stretch; padding: var(--space-3); box-shadow: var(--shadow-8);
  }
  .site-nav.is-open { display: flex; }
  .site-nav a { padding: var(--space-3); border-radius: var(--radius-md); }
  .sidebar {
    display: none; position: static; max-height: none; padding: var(--space-4);
    background: var(--color-bg-elevated); border: 1px solid var(--color-border); border-radius: var(--radius-lg);
  }
  .sidebar.is-open { display: block; }
}