* { box-sizing: border-box; }
    body {
      margin: 0;
      font-family: -apple-system, BlinkMacSystemFont, "Helvetica Neue", sans-serif;
      font-size: 17px;
      background: #f2f2f7;
      color: #111;
      line-height: 1.5;
      -webkit-text-size-adjust: 100%;
      text-size-adjust: 100%;
      -webkit-print-color-adjust: exact;
      print-color-adjust: exact;
    }
    .preview-page {
      max-width: 820px;
      margin: 0 auto;
      padding: 16px;
      display: flex;
      flex-direction: column;
      gap: 14px;
    }
    .card {
      background: #fff;
      border: 1px solid rgba(60, 60, 67, 0.2);
      border-radius: 14px;
      padding: 14px 12px;
      margin: 0;
      display: flex;
      flex-direction: column;
      gap: 8px;
    }
    .section-hero {
      margin: 0;
      display: flex;
      flex-direction: column;
      gap: 10px;
    }
    .card.card-h2 {
      padding: 14px 12px;
      gap: 8px;
      box-shadow: 0 4px 10px rgba(0, 0, 0, 0.14);
    }
    @media (prefers-color-scheme: dark) {
      .card.card-h2 {
        box-shadow: 0 4px 10px rgba(0, 0, 0, 0.32);
      }
      .heading-1 .title {
        color: #f2f2f7;
        -webkit-text-stroke-color: #000000;
      }
    }
    .segment { padding: 0; margin: 0; }
    .segment.embed { padding: 0; }
    .heading-1 { margin: 0; padding: 10px 0 8px; }
    .heading-1 .title {
      font-size: 34px;
      font-weight: 800;
      line-height: 1.15;
      margin: 0;
      color: #1c1c1e;
      -webkit-text-stroke: 2.5px #ffffff;
      paint-order: stroke fill;
      -webkit-print-color-adjust: exact;
      print-color-adjust: exact;
    }
    .heading-2 {
      display: flex;
      align-items: flex-start;
      gap: 10px;
      margin: 0;
      padding: 4px 0 2px;
      -webkit-print-color-adjust: exact;
      print-color-adjust: exact;
    }
    .heading-2 .marker {
      width: 4px;
      border-radius: 2px;
      background-color: rgb(115, 51, 191);
      flex-shrink: 0;
      align-self: stretch;
      min-height: 1.2em;
    }
    .heading-2 .title {
      font-size: 28px;
      font-weight: 700;
      line-height: 1.25;
      margin: 0;
      color: #1d1d1f;
      background-color: rgba(209, 184, 255, 0.85);
      box-decoration-break: clone;
      -webkit-box-decoration-break: clone;
      padding: 2px 6px 4px;
      display: inline;
    }
    .heading-3 {
      display: flex;
      align-items: flex-start;
      gap: 10px;
      margin: 0;
      padding: 10px 0 2px;
      -webkit-print-color-adjust: exact;
      print-color-adjust: exact;
    }
    .heading-3 .marker {
      width: 4px;
      border-radius: 2px;
      background-color: rgb(26, 102, 179);
      flex-shrink: 0;
      align-self: stretch;
      min-height: 1.1em;
    }
    .heading-3 .title {
      font-size: 20px;
      font-weight: 700;
      line-height: 1.3;
      margin: 0;
      color: #1d1d1f;
      background-color: rgba(188, 227, 255, 0.85);
      box-decoration-break: clone;
      -webkit-box-decoration-break: clone;
      padding: 2px 6px 3px;
      display: inline;
    }
    @media (prefers-color-scheme: dark) {
      .heading-3 .marker {
        background-color: rgb(107, 163, 250);
      }
      .heading-3 .title {
        color: #f5f5f7;
        background-color: rgba(66, 122, 230, 0.35);
      }
    }
    .heading-n {
      font-size: 20px;
      font-weight: 600;
      margin: 0;
    }
    .list-item {
      display: flex;
      align-items: baseline;
      gap: 8px;
      margin: 0;
    }
    .list-item .list-marker {
      flex-shrink: 0;
      color: rgba(60, 60, 67, 0.7);
    }
    .list-item .list-marker.bullet {
      width: 5px;
      height: 5px;
      border-radius: 50%;
      background: rgba(60, 60, 67, 0.6);
      margin-top: 0.55em;
    }
    .list-item .list-marker.ordered {
      min-width: 20px;
      text-align: right;
      font-variant-numeric: tabular-nums;
    }
    .list-item .list-marker.task {
      width: 16px;
      height: 16px;
      margin-top: 0.15em;
      accent-color: rgba(60, 60, 67, 0.85);
    }
    .list-item.task-checked .paragraph {
      color: rgba(60, 60, 67, 0.55);
      text-decoration: line-through;
    }
    .blockquote {
      margin: 0;
      padding: 8px 12px;
      border-left: 4px solid rgba(120, 120, 128, 0.45);
      color: rgba(60, 60, 67, 0.85);
    }
    .thematic-break {
      border: 0;
      border-top: 1px solid rgba(60, 60, 67, 0.25);
      margin: 8px 0;
    }
    .table-wrap {
      overflow-x: auto;
      border-radius: 8px;
      border: 1.5px solid rgba(60, 60, 67, 0.44);
      background: #fff;
      box-shadow: 0 4px 10px rgba(0, 0, 0, 0.12);
      max-width: 100%;
      display: inline-block;
    }
    @media (prefers-color-scheme: dark) {
      .table-wrap {
        border-color: rgba(255, 255, 255, 0.44);
        background: rgba(28, 28, 30, 0.92);
        box-shadow: 0 4px 10px rgba(0, 0, 0, 0.32);
      }
    }
    table.data-table {
      border-collapse: collapse;
      width: max-content;
      max-width: 100%;
      font-size: 15px;
      table-layout: auto;
    }
    table.data-table td {
      border: 1px solid rgba(60, 60, 67, 0.30);
      padding: 8px 10px;
      text-align: left;
      vertical-align: top;
      white-space: pre-wrap;
      word-break: break-word;
    }
    table.data-table th {
      border: 1px solid rgba(60, 60, 67, 0.30);
      padding: 8px 10px;
      text-align: left;
      vertical-align: top;
      white-space: pre-wrap;
      word-break: break-word;
      font-weight: 600;
      background: rgba(120, 120, 128, 0.12);
    }
    @media (prefers-color-scheme: dark) {
      table.data-table td {
        border-color: rgba(255, 255, 255, 0.30);
      }
      table.data-table th {
        border-color: rgba(255, 255, 255, 0.30);
        background: rgba(120, 120, 128, 0.18);
      }
    }
    .code-block-shell {
      background: rgba(120, 120, 128, 0.12);
      border-radius: 8px;
      overflow: hidden;
      margin: 0;
      border: 0.5px solid rgba(0, 0, 0, 0.10);
    }
    @media (prefers-color-scheme: dark) {
      .code-block-shell {
        border-color: rgba(255, 255, 255, 0.18);
      }
    }
    .code-block-toolbar {
      display: flex;
      align-items: center;
      justify-content: space-between;
      gap: 8px;
      padding: 6px 10px;
      background: rgba(120, 120, 128, 0.06);
      border-bottom: 0.5px solid rgba(0, 0, 0, 0.10);
    }
    @media (prefers-color-scheme: dark) {
      .code-block-toolbar {
        background: rgba(255, 255, 255, 0.06);
        border-bottom-color: rgba(255, 255, 255, 0.18);
      }
    }
    .code-block-lang {
      font-size: 11px;
      font-weight: 600;
      text-transform: lowercase;
      color: rgba(60, 60, 67, 0.7);
    }
    .code-copy-btn {
      font: 12px -apple-system, BlinkMacSystemFont, sans-serif;
      font-weight: 500;
      color: rgba(60, 60, 67, 0.7);
      background: transparent;
      border: 0;
      padding: 0;
      cursor: pointer;
    }
    .code-block {
      background: transparent;
      border-radius: 0;
      padding: 10px;
      overflow-x: auto;
      margin: 0;
      border: 0;
    }
    .code-block code {
      font-family: ui-monospace, SFMono-Regular, Menlo, monospace;
      font-size: 15px;
      white-space: pre-wrap;
      word-break: break-word;
    }
    .paragraph { margin: 0; line-height: 1.4; font-size: 17px; }
    .list-item { font-size: 17px; }
    .blockquote { font-size: 17px; }
    .embed-url {
      display: block;
      padding: 8px;
      border-radius: 8px;
      word-break: break-all;
      color: #0a58ca;
      text-decoration: none;
    }
    .embed-preview {
      border-radius: 8px;
      overflow: hidden;
      margin-top: 8px;
    }
    .embed-preview iframe {
      width: 100%;
      border: 0;
      display: block;
    }
    .embed-youtube { aspect-ratio: 16 / 9; }
    .embed-youtube iframe { height: 100%; min-height: 200px; }
    .embed-iframe iframe { height: 240px; }
    .embed-map iframe { height: 260px; }
    figure.mermaid-block {
      margin: 8px 0;
      padding: 10px 8px;
      border-radius: 8px;
      overflow-x: auto;
      border: 0.5px solid rgba(0, 0, 0, 0.10);
      background: rgba(120, 120, 128, 0.12);
    }
    @media (prefers-color-scheme: dark) {
      figure.mermaid-block {
        border-color: rgba(255, 255, 255, 0.18);
        background: rgba(120, 120, 128, 0.18);
      }
    }
    figure.mermaid-block img.mermaid-image {
      display: block;
      width: 100%;
      height: auto;
    }
    figure.mermaid-block .mermaid-message {
      margin: 0;
      font-size: 14px;
      line-height: 1.45;
      color: rgba(60, 60, 67, 0.72);
    }
    @media (prefers-color-scheme: dark) {
      figure.mermaid-block .mermaid-message {
        color: rgba(235, 235, 245, 0.72);
      }
    }
    figure.image-block {
      margin: 4px 0;
      border-radius: 10px;
      overflow: hidden;
      border: 1px solid rgba(0, 0, 0, 0.14);
      box-shadow: 0 4px 10px rgba(0, 0, 0, 0.12);
    }
    @media (prefers-color-scheme: dark) {
      figure.image-block {
        border-color: rgba(255, 255, 255, 0.22);
        box-shadow: 0 4px 10px rgba(0, 0, 0, 0.32);
      }
    }
    figure.image-block img,
    figure.image-block video {
      max-width: 100%;
      height: auto;
      display: block;
    }
    figure.image-block .embed-preview {
      max-width: 100%;
      display: block;
      border-radius: 0;
      overflow: hidden;
      margin: 0;
    }
    figure.image-block .embed-preview iframe {
      width: 100%;
      border: 0;
      display: block;
    }
    figure.image-block figcaption {
      font-size: 12px;
      margin: 0;
      padding: 6px 12px;
      background: rgba(0, 0, 0, 0.04);
      border-top: 1px solid rgba(0, 0, 0, 0.14);
    }
    @media (prefers-color-scheme: dark) {
      figure.image-block figcaption {
        background: rgba(255, 255, 255, 0.06);
        border-top-color: rgba(255, 255, 255, 0.22);
      }
    }
    figure.image-block a { color: #0a58ca; word-break: break-all; }
    a { color: #0a58ca; }
    /* ダークモード: 明るさ前提の値をまとめて反転する。
       個別の要素だけ暗い色に差し替えて本文色を据え置いていたため、
       暗い背景に暗い文字（#111）が乗って表が読めなくなっていた。 */
    @media (prefers-color-scheme: dark) {
      body {
        background: #000;
        color: #f2f2f7;
      }
      .card {
        background: rgba(28, 28, 30, 0.92);
        border-color: rgba(255, 255, 255, 0.18);
      }
      /* h3 には元からダーク指定があったが h2 だけ抜けていた（同じ扱いに揃える） */
      .heading-2 .marker { background-color: rgb(178, 132, 255); }
      .heading-2 .title {
        color: #f5f5f7;
        background-color: rgba(140, 96, 230, 0.35);
      }
      .list-item .list-marker { color: rgba(235, 235, 245, 0.60); }
      .list-item .list-marker.bullet { background: rgba(235, 235, 245, 0.50); }
      .list-item .list-marker.task { accent-color: rgba(235, 235, 245, 0.85); }
      .list-item.task-checked .paragraph { color: rgba(235, 235, 245, 0.45); }
      .blockquote {
        border-left-color: rgba(235, 235, 245, 0.35);
        color: rgba(235, 235, 245, 0.75);
      }
      .thematic-break { border-top-color: rgba(235, 235, 245, 0.25); }
      .code-block-lang,
      .code-copy-btn { color: rgba(235, 235, 245, 0.60); }
      figure.mermaid-block .mermaid-message { color: rgba(235, 235, 245, 0.62); }
      figure.image-block figcaption { background: rgba(255, 255, 255, 0.06); }
      .embed-url,
      figure.image-block a,
      a { color: #0a84ff; }
    }

    @media print {
      body { background: #fff; -webkit-print-color-adjust: exact; print-color-adjust: exact; }
      .preview-page { max-width: none; padding: 0; }
      .card { break-inside: avoid; box-shadow: none; }
      .heading-2 .marker,
      .heading-2 .title,
      .heading-3 .marker,
      .heading-3 .title,
      .heading-1 {
        -webkit-print-color-adjust: exact;
        print-color-adjust: exact;
      }
    }