body {
      display: flex;
      flex-direction: column;
      min-height: 100vh;
    }

    main {
      flex: 1;
      padding-top: calc(var(--nav-h) + 56px);
      padding-bottom: 96px;
    }

    /* ── ページヘッダー ── */
    .page-header {
      margin-bottom: 56px;
    }

    .page-header-inner {
      display: flex;
      flex-direction: column;
      gap: 20px;
    }

    .page-eyebrow {
      display: flex;
      align-items: center;
      gap: 14px;
    }

    .page-eyebrow-line {
      width: 32px;
      height: 1px;
      background: var(--accent-blue);
      opacity: 0.6;
    }

    .page-eyebrow-text {
      font-family: var(--font-mono);
      font-size: 0.60rem;
      color: var(--accent-teal);
      letter-spacing: 0.28em;
      text-transform: uppercase;
    }

    .page-desc {
      font-size: 0.88rem;
      color: var(--text-1);
      line-height: 1.85;
      max-width: 560px;
    }

    /* ── カテゴリタブ ── */
    .tab-bar {
      display: flex;
      gap: 0;
      border-bottom: 1px solid var(--border);
      margin-bottom: 48px;
      overflow-x: auto;
      scrollbar-width: none;
      -ms-overflow-style: none;
    }

    .tab-bar::-webkit-scrollbar { display: none; }

    .tab-btn {
      display: inline-flex;
      align-items: center;
      gap: 8px;
      font-family: var(--font-mono);
      font-size: 0.65rem;
      letter-spacing: 0.14em;
      text-transform: uppercase;
      color: var(--text-2);
      background: none;
      border: none;
      border-bottom: 2px solid transparent;
      padding: 12px 24px;
      cursor: pointer;
      white-space: nowrap;
      transition: color var(--t), border-color var(--t);
      min-height: 48px;
      margin-bottom: -1px;
    }

    .tab-btn:hover {
      color: var(--text-1);
    }

    .tab-btn.active {
      color: var(--text-0);
      border-bottom-color: var(--accent-blue);
    }

    .tab-btn[data-cat="physics"].active    { border-bottom-color: #3b9eff; color: #3b9eff; }
    .tab-btn[data-cat="astronomy"].active  { border-bottom-color: #00e5b8; color: #00e5b8; }
    .tab-btn[data-cat="mathematics"].active{ border-bottom-color: #8b72ff; color: #8b72ff; }
    .tab-btn[data-cat="simulations"].active{ border-bottom-color: #ffb340; color: #ffb340; }

    .tab-dot {
      width: 6px;
      height: 6px;
      border-radius: 50%;
      background: currentColor;
      opacity: 0.6;
      flex-shrink: 0;
    }

    /* ── カテゴリパネル ── */
    .cat-panel {
      display: none;
    }

    .cat-panel.active {
      display: block;
    }

    /* ── カテゴリ紹介バナー ── */
    .cat-banner {
      display: flex;
      align-items: center;
      gap: 28px;
      padding: 28px 32px;
      background: var(--bg-card);
      border: 1px solid var(--border);
      border-radius: var(--r-xl);
      backdrop-filter: blur(16px);
      -webkit-backdrop-filter: blur(16px);
      margin-bottom: 36px;
      position: relative;
      overflow: hidden;
    }

    .cat-banner::before {
      content: '';
      position: absolute;
      top: 0;
      left: 0;
      right: 0;
      height: 2px;
      border-radius: var(--r-xl) var(--r-xl) 0 0;
    }

    .cat-banner[data-cat="physics"]::before    { background: linear-gradient(90deg, #3b9eff, transparent); }
    .cat-banner[data-cat="astronomy"]::before  { background: linear-gradient(90deg, #00e5b8, transparent); }
    .cat-banner[data-cat="mathematics"]::before{ background: linear-gradient(90deg, #8b72ff, transparent); }
    .cat-banner[data-cat="simulations"]::before{ background: linear-gradient(90deg, #ffb340, transparent); }

    .cat-banner-icon {
      width: 56px;
      height: 56px;
      border-radius: var(--r-md);
      border: 1px solid var(--border);
      display: flex;
      align-items: center;
      justify-content: center;
      flex-shrink: 0;
    }

    .cat-banner-icon svg {
      width: 28px;
      height: 28px;
    }

    .cat-banner[data-cat="physics"]     .cat-banner-icon { background: rgba(59,158,255,0.06); color: #3b9eff; }
    .cat-banner[data-cat="astronomy"]   .cat-banner-icon { background: rgba(0,229,184,0.06);  color: #00e5b8; }
    .cat-banner[data-cat="mathematics"] .cat-banner-icon { background: rgba(139,114,255,0.06);color: #8b72ff; }
    .cat-banner[data-cat="simulations"] .cat-banner-icon { background: rgba(255,179,64,0.06); color: #ffb340; }

    .cat-banner-body {
      flex: 1;
    }

    .cat-banner-label {
      font-family: var(--font-mono);
      font-size: 0.58rem;
      letter-spacing: 0.24em;
      text-transform: uppercase;
      margin-bottom: 6px;
    }

    .cat-banner[data-cat="physics"]     .cat-banner-label { color: #3b9eff; }
    .cat-banner[data-cat="astronomy"]   .cat-banner-label { color: #00e5b8; }
    .cat-banner[data-cat="mathematics"] .cat-banner-label { color: #8b72ff; }
    .cat-banner[data-cat="simulations"] .cat-banner-label { color: #ffb340; }

    .cat-banner-title {
      font-family: var(--font-display);
      font-size: 1.25rem;
      font-weight: 800;
      letter-spacing: -0.02em;
      color: var(--text-0);
      margin-bottom: 6px;
    }

    .cat-banner-desc {
      font-size: 0.80rem;
      color: var(--text-1);
      line-height: 1.75;
    }

    .cat-banner-count {
      font-family: var(--font-mono);
      font-size: 0.60rem;
      color: var(--text-2);
      letter-spacing: 0.12em;
      flex-shrink: 0;
      text-align: right;
    }

    .cat-banner-count strong {
      display: block;
      font-family: var(--font-display);
      font-size: 1.8rem;
      font-weight: 800;
      letter-spacing: -0.04em;
      color: var(--text-0);
      line-height: 1;
      margin-bottom: 4px;
    }

    /* ── サブカテゴリフィルター ── */
    .subcat-bar {
      display: flex;
      flex-wrap: wrap;
      gap: 6px;
      margin-bottom: 28px;
    }

    .subcat-btn {
      font-family: var(--font-mono);
      font-size: 0.60rem;
      letter-spacing: 0.12em;
      text-transform: uppercase;
      padding: 6px 14px;
      border-radius: 99px;
      border: 1px solid var(--border);
      background: transparent;
      color: var(--text-2);
      cursor: pointer;
      transition: background var(--t), border-color var(--t), color var(--t);
      min-height: 32px;
    }

    .subcat-btn:hover {
      border-color: var(--border-m);
      color: var(--text-1);
    }

    .subcat-btn.active {
      border-color: var(--border-m);
      color: var(--text-0);
      background: rgba(255,255,255,0.04);
    }

    /* ── アイテムグリッド ── */
    .items-grid {
      display: grid;
      grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
      gap: 20px;
      margin-bottom: 32px;
    }

    /* ── スタディカード ── */
    .study-card {
      background: var(--bg-card);
      border: 1px solid var(--border);
      border-radius: var(--r-lg);
      backdrop-filter: blur(16px);
      -webkit-backdrop-filter: blur(16px);
      padding: 24px;
      display: flex;
      flex-direction: column;
      gap: 12px;
      text-decoration: none;
      color: inherit;
      transition:
        border-color var(--t),
        background var(--t),
        transform var(--t) var(--ease),
        box-shadow var(--t);
      position: relative;
      overflow: hidden;
    }

    .study-card::before {
      content: '';
      position: absolute;
      top: 0;
      left: 0;
      right: 0;
      height: 1px;
      opacity: 0;
      transition: opacity var(--t);
    }

    .study-card[data-cat="physics"]::before     { background: linear-gradient(90deg, #3b9eff, transparent); }
    .study-card[data-cat="astronomy"]::before   { background: linear-gradient(90deg, #00e5b8, transparent); }
    .study-card[data-cat="mathematics"]::before { background: linear-gradient(90deg, #8b72ff, transparent); }
    .study-card[data-cat="simulations"]::before { background: linear-gradient(90deg, #ffb340, transparent); }

    .study-card:hover {
      transform: translateY(-3px);
      border-color: var(--border-m);
      background: var(--bg-card-hover);
      box-shadow: 0 10px 32px rgba(0,0,0,0.3);
    }

    .study-card:hover::before {
      opacity: 1;
    }

    .card-meta {
      display: flex;
      align-items: center;
      justify-content: space-between;
    }

    .card-subcat {
      font-family: var(--font-mono);
      font-size: 0.56rem;
      letter-spacing: 0.16em;
      text-transform: uppercase;
      padding: 3px 10px;
      border-radius: 99px;
      border: 1px solid;
    }

    .study-card[data-cat="physics"]     .card-subcat { color: #3b9eff; border-color: rgba(59,158,255,0.25); background: rgba(59,158,255,0.06); }
    .study-card[data-cat="astronomy"]   .card-subcat { color: #00e5b8; border-color: rgba(0,229,184,0.25);  background: rgba(0,229,184,0.06); }
    .study-card[data-cat="mathematics"] .card-subcat { color: #8b72ff; border-color: rgba(139,114,255,0.25);background: rgba(139,114,255,0.06); }
    .study-card[data-cat="simulations"] .card-subcat { color: #ffb340; border-color: rgba(255,179,64,0.25); background: rgba(255,179,64,0.06); }

    .card-difficulty {
      display: flex;
      gap: 3px;
    }

    .diff-pip {
      width: 8px;
      height: 8px;
      border-radius: 2px;
      background: var(--border-m);
    }

    .diff-pip.filled[data-cat="physics"]     { background: #3b9eff; }
    .diff-pip.filled[data-cat="astronomy"]   { background: #00e5b8; }
    .diff-pip.filled[data-cat="mathematics"] { background: #8b72ff; }
    .diff-pip.filled[data-cat="simulations"] { background: #ffb340; }

    .study-card-title {
      font-family: var(--font-display);
      font-size: 1.00rem;
      font-weight: 800;
      letter-spacing: -0.02em;
      color: var(--text-0);
      line-height: 1.25;
    }

    .study-card-excerpt {
      font-size: 0.78rem;
      color: var(--text-1);
      line-height: 1.75;
      flex: 1;
    }

    .study-card-footer {
      display: flex;
      align-items: center;
      justify-content: space-between;
      padding-top: 12px;
      border-top: 1px solid var(--border);
    }

    .study-card-date {
      font-family: var(--font-mono);
      font-size: 0.58rem;
      color: var(--text-2);
      letter-spacing: 0.10em;
    }

    .study-card-arrow {
      width: 20px;
      height: 20px;
      color: var(--text-2);
      transition: color var(--t), transform var(--t) var(--ease-spring);
    }

    .study-card:hover .study-card-arrow {
      color: var(--accent-blue);
      transform: translateX(3px);
    }

    /* ── シミュレーションカード（特別デザイン） ── */
    .sim-card {
      background: var(--bg-card);
      border: 1px solid rgba(255,179,64,0.15);
      border-radius: var(--r-lg);
      backdrop-filter: blur(16px);
      -webkit-backdrop-filter: blur(16px);
      padding: 28px;
      display: flex;
      flex-direction: column;
      gap: 14px;
      text-decoration: none;
      color: inherit;
      position: relative;
      overflow: hidden;
      transition:
        border-color var(--t),
        background var(--t),
        transform var(--t) var(--ease),
        box-shadow var(--t);
    }

    .sim-card::before {
      content: '';
      position: absolute;
      top: 0; left: 0; right: 0;
      height: 1px;
      background: linear-gradient(90deg, #ffb340, transparent);
      opacity: 0;
      transition: opacity var(--t);
    }

    .sim-card:hover {
      transform: translateY(-3px);
      border-color: rgba(255,179,64,0.30);
      background: var(--bg-card-hover);
      box-shadow: 0 10px 32px rgba(0,0,0,0.3), 0 0 24px rgba(255,179,64,0.05);
    }

    .sim-card:hover::before { opacity: 1; }

    .sim-card-preview {
      width: 100%;
      height: 120px;
      background: rgba(2,8,20,0.8);
      border-radius: var(--r-sm);
      border: 1px solid rgba(255,179,64,0.12);
      display: flex;
      align-items: center;
      justify-content: center;
      overflow: hidden;
      position: relative;
    }

    .sim-preview-svg {
      width: 100%;
      height: 100%;
    }

    .sim-card-type {
      font-family: var(--font-mono);
      font-size: 0.56rem;
      letter-spacing: 0.18em;
      text-transform: uppercase;
      color: #ffb340;
      border: 1px solid rgba(255,179,64,0.25);
      background: rgba(255,179,64,0.06);
      border-radius: 99px;
      padding: 3px 10px;
      align-self: flex-start;
    }

    .sim-card-title {
      font-family: var(--font-display);
      font-size: 1.05rem;
      font-weight: 800;
      letter-spacing: -0.02em;
      color: var(--text-0);
      line-height: 1.25;
    }

    .sim-card-desc {
      font-size: 0.78rem;
      color: var(--text-1);
      line-height: 1.75;
      flex: 1;
    }

    .sim-card-tech {
      display: flex;
      flex-wrap: wrap;
      gap: 5px;
    }

    .sim-tech-tag {
      font-family: var(--font-mono);
      font-size: 0.54rem;
      letter-spacing: 0.10em;
      color: var(--text-2);
      border: 1px solid var(--border);
      border-radius: 4px;
      padding: 2px 7px;
    }

    .sim-card-footer {
      display: flex;
      align-items: center;
      justify-content: space-between;
      padding-top: 12px;
      border-top: 1px solid rgba(255,179,64,0.10);
    }

    .sim-card-status {
      font-family: var(--font-mono);
      font-size: 0.58rem;
      color: #ffb340;
      letter-spacing: 0.12em;
      display: flex;
      align-items: center;
      gap: 5px;
    }

    .sim-card-status-dot {
      width: 5px;
      height: 5px;
      border-radius: 50%;
      background: #ffb340;
      animation: statusPulse 2.5s ease-in-out infinite;
    }

    .sim-card-open {
      font-family: var(--font-mono);
      font-size: 0.58rem;
      color: var(--text-2);
      display: flex;
      align-items: center;
      gap: 4px;
      transition: color var(--t);
    }

    .sim-card:hover .sim-card-open { color: #ffb340; }

    .sim-card-open svg {
      width: 14px;
      height: 14px;
      transition: transform var(--t) var(--ease-spring);
    }

    .sim-card:hover .sim-card-open svg { transform: translateX(3px); }

    @keyframes statusPulse {
      0%, 100% { opacity: 1; }
      50%       { opacity: 0.25; }
    }

    /* ── 空の状態 ── */
    .empty-state {
      grid-column: 1 / -1;
      display: flex;
      flex-direction: column;
      align-items: center;
      gap: 14px;
      padding: 72px 32px;
      text-align: center;
    }
    .empty-state-icon {
      display: none;
    }
    .empty-badge {
      order: -1;
      font-family: var(--font-display);
      font-size: clamp(1.6rem, 4vw, 2.4rem);
      font-weight: 800;
      background: linear-gradient(135deg, var(--accent-teal), var(--accent-blue));
      -webkit-background-clip: text;
      background-clip: text;
      -webkit-text-fill-color: transparent;
      border: none;
      background-color: transparent;
      padding: 0;
      letter-spacing: 0.02em;
      text-transform: none;
      margin-bottom: 4px;
    }
    .empty-title {
      font-family: var(--font-display);
      font-size: 1.05rem;
      font-weight: 700;
      color: var(--text-1);
    }
    .empty-desc {
      font-size: 0.80rem;
      color: var(--text-2);
      line-height: 1.75;
      max-width: 360px;
    }

    /* ── ローディング ── */
    .loading-state {
      display: flex;
      align-items: center;
      justify-content: center;
      gap: 10px;
      padding: 80px 0;
      font-family: var(--font-mono);
      font-size: 0.70rem;
      color: var(--text-2);
      letter-spacing: 0.14em;
    }

    .loading-dot {
      width: 6px;
      height: 6px;
      border-radius: 50%;
      background: var(--accent-blue);
      animation: loadingPulse 1.2s ease-in-out infinite;
    }

    .loading-dot:nth-child(2) { animation-delay: 0.2s; }
    .loading-dot:nth-child(3) { animation-delay: 0.4s; }

    @keyframes loadingPulse {
      0%, 80%, 100% { transform: scale(0.5); opacity: 0.3; }
      40%            { transform: scale(1.0); opacity: 1.0; }
    }

    /* ── 戻るリンク ── */
    .back-to-lab {
      display: inline-flex;
      align-items: center;
      gap: 10px;
      font-family: var(--font-mono);
      font-size: 0.62rem;
      color: var(--text-2);
      letter-spacing: 0.14em;
      text-transform: uppercase;
      text-decoration: none;
      transition: color var(--t);
      margin-top: 56px;
    }

    .back-to-lab:hover { color: var(--accent-blue); }

    .back-to-lab svg {
      width: 14px;
      height: 14px;
      transform: rotate(180deg);
    }

    /* ── レスポンシブ ── */
    @media (max-width: 760px) {
      main { padding-top: calc(var(--nav-h) + 36px); }
      .items-grid { grid-template-columns: 1fr; }
      .cat-banner { flex-direction: column; align-items: flex-start; gap: 16px; padding: 20px; }
      .cat-banner-count { text-align: left; }
      .tab-btn { padding: 12px 16px; font-size: 0.58rem; }
    }

    .error-state {
      display: none;
      text-align: center;
      padding: 80px 0;
    }

    .error-state-text {
      max-width: 420px;
      margin: 0 auto 18px;
      color: var(--text-1);
      font-size: var(--fs-xs);
      line-height: 1.8;
    }

    .retry-btn {
      display: inline-flex;
      align-items: center;
      gap: 8px;
      padding: 10px 22px;
      border-radius: var(--r-sm);
      border: 1px solid var(--border-m);
      background: rgba(75,169,255,0.08);
      color: var(--accent-blue);
      font-family: var(--font-mono);
      font-size: var(--fs-xs);
      letter-spacing: var(--ls-wide);
      cursor: pointer;
      transition: background var(--t), border-color var(--t), transform var(--t) var(--ease-spring);
      min-height: 42px;
    }

    .retry-btn:hover {
      background: rgba(75,169,255,0.16);
      border-color: var(--accent-blue);
      transform: translateY(-2px);
    }

    .retry-btn svg { width: 14px; height: 14px; }

    /* ══════ Astronomy統合コンテンツ（Studyタブ内） ══════ */
    .astro-fact-strip {
      display: grid;
      grid-template-columns: repeat(4, 1fr);
      gap: 1px;
      background: var(--border);
      border: 1px solid var(--border);
      border-radius: var(--r-lg);
      overflow: hidden;
      margin-bottom: 28px;
    }

    .astro-fact-item {
      background: var(--bg-card);
      padding: 18px 12px;
      text-align: center;
    }

    .astro-fact-value {
      font-family: var(--font-display);
      font-size: 1.3rem;
      font-weight: 800;
      color: var(--accent-teal);
      margin-bottom: 4px;
    }

    .astro-fact-label {
      font-family: var(--font-mono);
      font-size: 0.54rem;
      color: var(--text-2);
      letter-spacing: var(--ls-wide);
      text-transform: uppercase;
      line-height: 1.4;
    }

    .astro-banner {
      display: flex;
      align-items: center;
      gap: 20px;
      padding: 22px 26px;
      background: var(--bg-card);
      border: 1px solid rgba(30,235,192,0.18);
      border-radius: var(--r-lg);
      margin-bottom: 28px;
      flex-wrap: wrap;
    }

    .astro-banner-badge {
      font-family: var(--font-mono);
      font-size: 0.54rem;
      color: var(--accent-teal);
      letter-spacing: var(--ls-wide);
      text-transform: uppercase;
      border: 1px solid rgba(30,235,192,0.25);
      background: rgba(30,235,192,0.06);
      border-radius: 99px;
      padding: 3px 10px;
      display: inline-block;
      margin-bottom: 8px;
    }

    .astro-banner-title {
      font-family: var(--font-display);
      font-size: 1.05rem;
      font-weight: 800;
      color: var(--text-0);
      margin-bottom: 6px;
    }

    .astro-banner-desc {
      font-size: var(--fs-xs);
      color: var(--text-1);
      line-height: 1.75;
      max-width: 460px;
    }

    .astro-banner-link {
      margin-left: auto;
      display: inline-flex;
      align-items: center;
      gap: 7px;
      font-family: var(--font-mono);
      font-size: var(--fs-2xs);
      color: var(--accent-teal);
      border: 1px solid rgba(30,235,192,0.28);
      background: rgba(30,235,192,0.05);
      border-radius: var(--r-sm);
      padding: 8px 16px;
      text-decoration: none;
      white-space: nowrap;
      transition: background var(--t), transform var(--t) var(--ease-spring);
    }

    .astro-banner-link:hover { background: rgba(30,235,192,0.12); transform: translateY(-2px); }
    .astro-banner-link svg { width: 13px; height: 13px; }

    .astro-subhead {
      font-family: var(--font-mono);
      font-size: 0.56rem;
      color: var(--accent-teal);
      letter-spacing: var(--ls-wide);
      text-transform: uppercase;
      margin: 32px 0 14px;
      padding-bottom: 8px;
      border-bottom: 1px solid var(--border);
    }

    .astro-catalog-grid {
      display: grid;
      grid-template-columns: repeat(auto-fill, minmax(240px, 1fr));
      gap: 16px;
      margin-bottom: 8px;
    }

    .astro-catalog-card {
      background: var(--bg-card);
      border: 1px solid var(--border);
      border-radius: var(--r-md);
      overflow: hidden;
    }

    .astro-catalog-preview {
      width: 100%;
      height: 100px;
      background: rgba(2,8,20,0.9);
    }

    .astro-catalog-preview svg { width: 100%; height: 100%; }

    .astro-catalog-body { padding: 14px 16px; }

    .astro-catalog-name {
      font-family: var(--font-display);
      font-size: 0.90rem;
      font-weight: 800;
      color: var(--text-0);
      margin-bottom: 6px;
    }

    .astro-catalog-desc {
      font-size: 0.72rem;
      color: var(--text-1);
      line-height: 1.65;
    }

    .astro-obs-empty {
      background: var(--bg-card);
      border: 1px solid var(--border);
      border-radius: var(--r-md);
      padding: 28px 24px;
      text-align: center;
      color: var(--text-2);
      font-family: var(--font-mono);
      font-size: var(--fs-xs);
      line-height: 1.85;
    }

    .astro-obs-empty strong { color: var(--accent-teal); }

    .astro-sim-grid {
      display: grid;
      grid-template-columns: repeat(auto-fill, minmax(220px, 1fr));
      gap: 14px;
    }

    .astro-sim-card {
      background: var(--bg-card);
      border: 1px solid var(--border);
      border-radius: var(--r-md);
      padding: 16px;
      opacity: 0.6;
    }

    .astro-sim-card-label {
      font-family: var(--font-mono);
      font-size: 0.52rem;
      letter-spacing: var(--ls-wide);
      color: var(--accent-amber);
      text-transform: uppercase;
      display: block;
      margin-bottom: 8px;
    }

    .astro-sim-card-name {
      font-family: var(--font-display);
      font-size: 0.86rem;
      font-weight: 700;
      color: var(--text-0);
      margin-bottom: 6px;
    }

    .astro-sim-card-desc {
      font-size: 0.70rem;
      color: var(--text-2);
      line-height: 1.6;
    }

    @media (max-width: 600px) {
      .astro-fact-strip { grid-template-columns: repeat(2, 1fr); }
      .astro-banner { flex-direction: column; align-items: flex-start; }
      .astro-banner-link { margin-left: 0; align-self: flex-start; }
    }