# こたえを逆さまに刷った小学生ドリル

> ドリルのシリーズから2ページ。算数は横組み、国語は縦組みで、どの問題の下にもこたえを逆さまに刷ります。

- HTML版: https://postext.dev/ja/cookbook/japanese-drill-upside-down-answers
- レシピ No. 172 · 教科書 · 難易度 2 (中級) · 出力: Canvas, PDF
- ジャンル: ワークブックと練習問題, 教科書
- 必要なもの postext ≥ 1.59.0, postext-pdf ≥ 1.59.0 · テスト環境 1.59.0, postext-pdf 1.59.0 ／テスト日 2026-10-24
- ページ: [1](https://postext.dev/cookbook/japanese-drill-upside-down-answers/ja/p01.webp?v=4fd772fe), [2](https://postext.dev/cookbook/japanese-drill-upside-down-answers/ja/p02.webp?v=4fd772fe), [1](https://postext.dev/cookbook/japanese-drill-upside-down-answers/ja/p03.webp?v=4fd772fe), [2](https://postext.dev/cookbook/japanese-drill-upside-down-answers/ja/p04.webp?v=4fd772fe)
- Sandboxで開く: https://postext.dev/ja/sandbox#recipe=japanese-drill-upside-down-answers&lang=ja (.postext: https://postext.dev/cookbook/japanese-drill-upside-down-answers/ja/japanese-drill-upside-down-answers.postext)
- 最終更新: 2026-10-24
- 他の言語: [en](https://postext.dev/en/cookbook/japanese-drill-upside-down-answers.md), [es](https://postext.dev/es/cookbook/japanese-drill-upside-down-answers.md), [ca](https://postext.dev/ca/cookbook/japanese-drill-upside-down-answers.md), [de](https://postext.dev/de/cookbook/japanese-drill-upside-down-answers.md), [fr](https://postext.dev/fr/cookbook/japanese-drill-upside-down-answers.md), [it](https://postext.dev/it/cookbook/japanese-drill-upside-down-answers.md), [pt](https://postext.dev/pt/cookbook/japanese-drill-upside-down-answers.md), [zh](https://postext.dev/zh/cookbook/japanese-drill-upside-down-answers.md), [ar](https://postext.dev/ar/cookbook/japanese-drill-upside-down-answers.md)

## かんたんな説明

小学生向けのドリルです。1ページは計算、□、記号でえらぶ問題、○×、もう1ページは漢字と読みを縦に組みます。問題ごとにこたえが逆さまに刷ってあり、子どもは本を回して答え合わせをします。

## できあがり

B5判、3年生向けドリルのシリーズから2ページを組みます。算数のページは横組みです。水色の帯に教科のラベル、題、マスコットのたぬき。その下に名前の線と点数の枠があり、答えの位ごとに□を置いたひっ算、6つの計算のあとの□、横に並んだア イ ウの選択肢、行末に（　）がある○×の問題、式を書く線がついた文章題2問と続きます。漢字のページは国語のドリルの刷り方どおり、上から下へ、右から左へ縦組みにします。読みを見て□に漢字を書く問題、線を引いたことばの読みを（　）に書く問題、正しいほうを○でかこむ問題、意味をえらぶ問題です。どの問題の下にも、こたえを灰色の小さな字で逆さまに刷ります。子どもにはこたえの場所が見えますが、ちらっと見ただけでは読めません。答え合わせのときに本を回します。

**このレシピが答える問い:**

- ドリルの問題ごとに、こたえを逆さまにして下に刷るにはどうしますか？
- 横組みと同じデザインで、縦組みのドリルのページを組むには？
- わり算の筆算を国ごとの学校の書き方で組むには？

## 手短な答え

```js
// script.js, 行 35–55
// `placement: 'inverted'` sets each exercise's key right after it in a box turned 180°: the
// pupil sees where the answers are without reading them, and turns the book to check. The
// key's words come from the exercise (the options' katakana, ○ and ×, the operations), so
// the Markdown holds nothing twice.
const drill = {
  id: 'drill',
  number: { shape: 'square', fontFamily: TEXT, fontWeight: 600, background: col('blue') },
  instruction: { fontFamily: ROUND, bold: false },
  options: { layout: 'row' }, // ア イ ウ side by side (the default labels in Japanese)
  trueFalse: { look: 'bracket' }, // （　） for ○ or ×
  blank: { look: 'box', width: 'answer', color: col('rule') }, // □ to write in
  area: { kind: 'lines', color: col('rule') },
  grid: { rule: col('rule') },
  solutions: { placement: 'inverted', box: 'kotae' },
  marginTop: em(1.1), marginBottom: em(0.4),
};
const kotae = { id: 'kotae', title: '', backgroundEnabled: false, border: { enabled: false },
  padding: { top: pt(0), right: pt(0), bottom: pt(0), left: pt(0) },
  body: { fontFamily: ROUND, fontSize: pt(8), lineHeight: pt(12), color: col('muted'),
    firstLineIndent: pt(0) },
  marginTop: mm(1), marginBottom: mm(2), keepTogether: true };
```

## 材料

**学べること**

- [解答](https://postext.dev/ja/docs/exercises.md#解答): 解答をどこに印刷するか。なし、各問の後、問の下に逆さま、章末、:::solutions の行の位置。
- [練習問題のスタイル](https://postext.dev/ja/docs/exercises.md#練習問題スタイル): exerciseStyles。練習問題の組み方を決める。番号（丸、四角、見出し語）、指示文、選択肢の記号、空欄、正誤の欄、線結びの点、語群、解答欄、マス目、活動アイコン、難易度。
- [縦組み](https://postext.dev/ja/docs/configuration-page-layout.md#縦組み): 中国語と日本語を上から下へ、右から読む行で組みます（layout.writingMode 'vertical-rl'）。段組みは上下に積む段になり、図と表は正立したまま、約物は縦組み用の字形になります。

**ほかに使うもの**

- [練習問題](https://postext.dev/ja/docs/exercises.md#練習問題)
- [筆算](https://postext.dev/ja/docs/exercises.md#筆算)
- [穴埋めと語群](https://postext.dev/ja/docs/exercises.md#穴埋めと語群)
- [選択問題と正誤問題](https://postext.dev/ja/docs/exercises.md#選択問題と正誤問題)
- [記述問題と解答欄](https://postext.dev/ja/docs/exercises.md#記述問題と解答欄)
- [仮名、漢字、ローマ字](https://postext.dev/ja/docs/japanese-layout.md#漢字かなローマ字)
- [中国語・日本語・韓国語のフォント](https://postext.dev/ja/docs/configuration-pdf-output.md#中国語日本語韓国語のフォント)
- [傍線](https://postext.dev/ja/docs/japanese-layout.md#傍線)
- [右綴じの本](https://postext.dev/ja/docs/configuration-page-layout.md#綴じ)
- [インラインのチップ](https://postext.dev/ja/docs/configuration-styles.md#チップスタイル)
- [3段以上の段組み](https://postext.dev/ja/docs/configuration-page-layout.md#レイアウトの種類)
- [デザインした章扉](https://postext.dev/ja/docs/configuration-headings.md#幅と詳細デザイン)
- [見出しの属性](https://postext.dev/ja/docs/document-format.md#見出しの属性)
- [ページデザインの画像](https://postext.dev/ja/docs/configuration-headers-footers.md#画像要素)
- [デザイン要素の基準位置](https://postext.dev/ja/docs/configuration-headers-footers.md#要素の配置)
- [セマンティックカラーパレット](https://postext.dev/ja/docs/configuration-fonts-colors-viewers.md#カラーパレット)
- [PDFの書き出し](https://postext.dev/ja/docs/configuration-pdf-output.md#pdfの生成)
- [囲みの中や本文中の段組み](https://postext.dev/ja/docs/document-format-directives.md#columns)
- [分割する囲み、分割しない囲み](https://postext.dev/ja/docs/configuration-callouts.md#calloutコンテナー)
- [中国語の改行](https://postext.dev/ja/docs/configuration-east-asian.md#東アジアの組版)
- [段末そろえ](https://postext.dev/ja/docs/configuration-page-flow.md#段末そろえ)
- [段落スタイル](https://postext.dev/ja/docs/configuration-styles.md#段落スタイル)
- [PDFに埋め込むフォント](https://postext.dev/ja/docs/configuration-pdf-output.md#なぜフォントプロバイダーが必要か)
- [リソースとしての図と表](https://postext.dev/ja/docs/document-format-resources.md#リソース)

**設定の一覧**

- [`bodyText`](https://postext.dev/ja/docs/configuration-text.md#本文), [`calloutStyles`](https://postext.dev/ja/docs/configuration-callouts.md#囲みスタイル), [`chipStyles`](https://postext.dev/ja/docs/configuration-styles.md#チップスタイル), [`colorPalette`](https://postext.dev/ja/docs/configuration-fonts-colors-viewers.md#カラーパレット), `exerciseStyles`, [`footer`](https://postext.dev/ja/docs/configuration-headers-footers.md#柱とノンブル), [`header`](https://postext.dev/ja/docs/configuration-headers-footers.md#柱とノンブル), [`headings`](https://postext.dev/ja/docs/configuration-headings.md#見出し), [`layout`](https://postext.dev/ja/docs/configuration-page-layout.md#レイアウト), [`locale`](https://postext.dev/ja/docs/configuration-language.md#ハイフネーション), [`orderedLists`](https://postext.dev/ja/docs/configuration-lists-math.md#番号付きリスト), [`page`](https://postext.dev/ja/docs/configuration-page-layout.md#ページ), [`paragraphStyles`](https://postext.dev/ja/docs/configuration-styles.md#段落スタイル)

**API**

- [`buildDocument`](https://postext.dev/ja/docs/configuration-programmatic-usage.md#文書のビルド), [`decompressWoff2`](https://postext.dev/ja/docs/configuration-pdf-output.md#ブラウザー向けフォントプロバイダーfontsource--woff2), `loadVerticalAlternates`, [`registerResourceImage`](https://postext.dev/ja/docs/architecture.md#apiの概要), [`renderPageToCanvas`](https://postext.dev/ja/docs/configuration-programmatic-usage.md#ページをビットマップに描画する), [`renderToPdf`](https://postext.dev/ja/docs/configuration-pdf-output.md#pdfの生成), [`withLoadedFonts`](https://postext.dev/ja/docs/configuration-programmatic-usage.md#レイアウトの前にフォントを読み込む)

**書体**

- Klee One (OFL-1.1), Zen Maru Gothic (OFL-1.1)

## 作り方

### 1 · 問題ごとのこたえを逆さまにする

コードは上の[手短な答え](https://postext.dev/ja/cookbook/japanese-drill-upside-down-answers.md#手短な答え)にあります。`placement: 'inverted'` は、各問題のすぐあとに、こたえを180°回した囲みで置きます。この囲みは問題自身の囲みの中に入るので、改ページで問題とこたえが離れることはありません。こたえは問題から作ります。計算とその答え、正しい選択肢のカタカナ、○と×、穴うめのことばです。こたえの囲みスタイル `kotae` は、字を小さく灰色にするだけです。

### 2 · 横組みにも縦組みにも使える帯

```js
// script.js, 行 59–76
// A heading design on a vertical page is laid along its column: x runs down the page and y
// to the left, so the same band stands at the right edge, from head to foot.
const BAND = 30; // mm: the band's depth (its height across, its width down)
const header = { enabled: true, minHeight: mm(BAND + 3), slot: { elements: [
  { kind: 'box', id: 'band', reserve: false, style: { backgroundColor: col('tint'),
    borderRadius: mm(4) }, placement: { anchor: { to: 'container', edge: 'top-left' },
    size: { width: 'fill', height: mm(BAND) } } },
  { kind: 'image', id: 'mascot', resourceId: '{attr.pic}', decorative: true, reserve: false,
    placement: { anchor: { to: 'container', edge: 'top-right' }, offset: { x: mm(-4), y: mm(1) },
      size: { width: mm(28), height: mm(28) } } },
  { kind: 'text', id: 'subject', content: '{attr.kicker}', fontFamily: ROUND, fontSize: pt(10),
    fontWeight: 700, color: col('ink'), box: { backgroundColor: col('sun'), borderRadius: mm(3),
      padding: { top: mm(0.6), bottom: mm(0.6), left: mm(2.4), right: mm(2.4) } },
    placement: { anchor: { to: 'container', edge: 'top-left' }, offset: { x: mm(5), y: mm(5) } } },
  { kind: 'text', id: 'title', content: '{titleText}', fontFamily: ROUND, fontSize: pt(20),
    fontWeight: 700, color: col('ink'),
    placement: { anchor: { to: '#subject', edge: 'below' }, offset: { x: mm(0), y: mm(2.5) } } },
] } };
```

縦組みのページでは、見出しのデザインは行に沿って置かれます。xはページの下へ、yは左へ進みます。`top-left` に固定して全幅にした帯は、算数のページでは上端に、漢字のページでは右端に立ちます。`top-right` に固定したマスコットは、どちらのページでも帯の終わりに来ます。デザインのどこにも、向きは書いてありません。

### 3 · ひとつの原稿から2冊のドリル

```js
// script.js, 行 271–279
// Two drill books of one series: arithmetic across, bound on the left; kanji in columns,
// bound on the right (vertical text binds there by itself).
const [sansu, kokugo] = markdown.split(/(?=^# 春のことば)/m);
const build = (text) => withLoadedFonts(() => buildDocument({ markdown: text, resources },
  config()), { ...kitFonts(FONTS), text: markdown });
const across = await build(sansu);
// 国語 is set in columns, top to bottom, right to left: the same design, turned.
writingMode = 'vertical-rl';
const docs = [across, await build(kokugo)];
```

設定は関数なので、組むたびに別のオブジェクトができます。2冊の違いは `writingMode` だけです。縦組みにすると、国語のドリルはそれだけで右綴じになります。`showBook` は2冊を背の左右に分けて並べます。本文は教科書体の Klee One、ラベルは Zen Maru Gothic です。どちらも縦組み用の約物を読み込み、漢字のページのかっこに使います。

## レシピの全体

レシピのフォルダーから合成した1つのファイルで、サンプルのテキストとレシピ集の共通キットを埋め込んであり、自分でページを組み立てます。動かすには、空のページの`<script type="module">`に入れるか、新しいCodePenのpenのJSパネルに貼り付けます（モジュールとして）。esm.shからpostextを読み込むので、インストールもビルドも要りません。

- レシピのフォルダー: https://github.com/drnachio/postext/tree/main/cookbook/japanese-drill-upside-down-answers

### script.js

```js
// ═══ Postext Cookbook · Nº 172 · A Japanese drill with the answers upside down ═══
// https://postext.dev/en/cookbook/japanese-drill-upside-down-answers
// Code: MIT · Text: original (CC BY 4.0) · Pictures: generated with diffusion models
// Fonts: Klee One, Zen Maru Gothic (SIL OFL 1.1) · Needs postext ≥ 1.59.0
import {
  buildDocument, withLoadedFonts, renderPageToCanvas, registerResourceImage,
  loadVerticalAlternates,
} from 'https://esm.sh/postext';
import { renderToPdf, decompressWoff2 } from 'https://esm.sh/postext-pdf';

const LANG = 'ja'; // @lang: the language of the frame; the drill is Japanese in all
const RECIPE = 'japanese-drill-upside-down-answers';

// ─── 1 · Design ─────────────────────────────────────────────────────────────
// #region palette: a drill book's blue, a warm yellow and a pale sky for the band
const palette = {
  ink: '#23272c', // text
  blue: '#2a6cb0', // the accent: exercise numbers, the title band's rule, the score box
  sun: '#f2c14e', // the subject badge
  tint: '#eaf2fb', // the title band
  rule: '#a8bfd8', // writing lines and boxes
  muted: '#69717b', // folios, the name line, the upside-down answers
  paper: '#ffffff',
};
const col = (id) => ({ hex: palette[id], model: 'hex', paletteId: id });
const colorPalette = [
  ...Object.entries(palette).map(([id, hex]) => ({ id, name: id, value: { hex, model: 'hex' } })),
  { id: 'main-color', name: 'accent (defaults)', value: { hex: palette.blue, model: 'hex' } },
];
// #endregion
// 教科書体 for the text a child copies from, a round gothic for the labels.
const [TEXT, ROUND] = ['Klee One', 'Zen Maru Gothic'];

// #region answer: the answers printed upside down under each exercise
// `placement: 'inverted'` sets each exercise's key right after it in a box turned 180°: the
// pupil sees where the answers are without reading them, and turns the book to check. The
// key's words come from the exercise (the options' katakana, ○ and ×, the operations), so
// the Markdown holds nothing twice.
const drill = {
  id: 'drill',
  number: { shape: 'square', fontFamily: TEXT, fontWeight: 600, background: col('blue') },
  instruction: { fontFamily: ROUND, bold: false },
  options: { layout: 'row' }, // ア イ ウ side by side (the default labels in Japanese)
  trueFalse: { look: 'bracket' }, // （　） for ○ or ×
  blank: { look: 'box', width: 'answer', color: col('rule') }, // □ to write in
  area: { kind: 'lines', color: col('rule') },
  grid: { rule: col('rule') },
  solutions: { placement: 'inverted', box: 'kotae' },
  marginTop: em(1.1), marginBottom: em(0.4),
};
const kotae = { id: 'kotae', title: '', backgroundEnabled: false, border: { enabled: false },
  padding: { top: pt(0), right: pt(0), bottom: pt(0), left: pt(0) },
  body: { fontFamily: ROUND, fontSize: pt(8), lineHeight: pt(12), color: col('muted'),
    firstLineIndent: pt(0) },
  marginTop: mm(1), marginBottom: mm(2), keepTogether: true };
// #endregion

// #region header: the drill's band: subject badge, title, the mascot at the far end
// A heading design on a vertical page is laid along its column: x runs down the page and y
// to the left, so the same band stands at the right edge, from head to foot.
const BAND = 30; // mm: the band's depth (its height across, its width down)
const header = { enabled: true, minHeight: mm(BAND + 3), slot: { elements: [
  { kind: 'box', id: 'band', reserve: false, style: { backgroundColor: col('tint'),
    borderRadius: mm(4) }, placement: { anchor: { to: 'container', edge: 'top-left' },
    size: { width: 'fill', height: mm(BAND) } } },
  { kind: 'image', id: 'mascot', resourceId: '{attr.pic}', decorative: true, reserve: false,
    placement: { anchor: { to: 'container', edge: 'top-right' }, offset: { x: mm(-4), y: mm(1) },
      size: { width: mm(28), height: mm(28) } } },
  { kind: 'text', id: 'subject', content: '{attr.kicker}', fontFamily: ROUND, fontSize: pt(10),
    fontWeight: 700, color: col('ink'), box: { backgroundColor: col('sun'), borderRadius: mm(3),
      padding: { top: mm(0.6), bottom: mm(0.6), left: mm(2.4), right: mm(2.4) } },
    placement: { anchor: { to: 'container', edge: 'top-left' }, offset: { x: mm(5), y: mm(5) } } },
  { kind: 'text', id: 'title', content: '{titleText}', fontFamily: ROUND, fontSize: pt(20),
    fontWeight: 700, color: col('ink'),
    placement: { anchor: { to: '#subject', edge: 'below' }, offset: { x: mm(0), y: mm(2.5) } } },
] } };
// #endregion

let writingMode = 'horizontal-tb'; // 算数 runs across the page
const config = () => ({
  locale: 'ja',
  colorPalette,
  page: { sizePreset: 'custom', width: mm(182), height: mm(257), dpi: 150, // B5
    margins: { top: mm(18), bottom: mm(16), left: mm(16), right: mm(16), mirror: true } },
  layout: { layoutType: 'single', writingMode },
  bodyText: { fontFamily: TEXT, fontSize: pt(12), lineHeight: pt(22), color: col('ink'),
    boldColor: col('ink'), italicColor: col('ink'), referenceColor: col('ink'),
    boldFontWeight: 600, // Klee One's heaviest cut
    textAlign: 'left', firstLineIndent: pt(0) },
  headings: { fontFamily: ROUND, color: col('ink'), fontWeight: 700, balancing: { enabled: false },
    levels: [{ level: 1, fontSize: pt(20), breakBefore: { parity: 'any' }, marginBottom: pt(0),
      advancedDesign: header }] },
  orderedLists: { numberFormat: 'arabic', color: col('ink'), fontWeight: 600 },
  paragraphStyles: [
    { id: 'namae', fontFamily: ROUND, fontSize: pt(10), color: col('muted'), textAlign: 'right',
      firstLineIndent: pt(0), marginTop: pt(0), marginBottom: mm(1) },
    { id: 'colophon', fontFamily: ROUND, fontSize: pt(7.5), lineHeight: pt(11), color: col('muted'),
      textAlign: 'left', firstLineIndent: pt(0), marginTop: mm(5) },
  ],
  chipStyles: [{ id: 'sen', backgroundEnabled: false, underline: 'solid', borderWidth: pt(0.7),
    borderColor: col('muted'), minWidth: mm(40), paddingX: pt(0), paddingY: pt(0) },
  { id: 'waku', backgroundEnabled: false, borderWidth: pt(1), borderColor: col('blue'),
    borderRadius: mm(1.5), minWidth: mm(16), paddingY: em(0.2) }],
  calloutStyles: [kotae],
  exerciseStyles: [drill],
  header: { elements: [] },
  footer: { elements: [{ kind: 'text', id: 'folio', content: '{pageNumber}', fontFamily: ROUND,
    fontSize: pt(9), fontWeight: 700, color: col('blue'), align: 'center',
    placement: { anchor: { to: 'page', edge: 'bottom' }, offset: { x: mm(0), y: mm(-9) } } }] },
});

// ─── 2 · Content ────────────────────────────────────────────────────────────
const markdown = String.raw`---
title: "3年生のまいにちドリル"
---

# 3けたのたし算とひき算 {kicker="さんすう　12" pic="tanuki"}

:::paragraphs{style="namae"}
名前:chip[　]{style="sen"}　　:chip[　]{style="waku"}点
:::

:::exercise{type=arithmetic}
ひっ算でしましょう。（1つ5点）

- 345 + 278
- 902 - 456
- 124 × 3
- 864 ÷ 4
:::

:::exercise
□にあてはまる数を書きましょう。（1つ5点）

:::columns{count=2}
25 + 37 = [[62]]

90 − 46 = [[44]]

8 × 7 = [[56]]

400 + 600 = [[1000]]

1000 − 1 = [[999]]

63 ÷ 9 = [[7]]
:::
:::

:::exercise{columns=3}
正しいものをえらんで、記号で答えましょう。（1つ5点）

1. 1000は、100を何こ集めた数ですか。
   - [ ] 1こ
   - [x] 10こ
   - [ ] 100こ
2. 500円玉を2まい出すと、何円ですか。
   - [ ] 700円
   - [ ] 520円
   - [x] 1000円
:::

:::exercise{type=truefalse}
正しいものには○、まちがっているものには×を書きましょう。（1つ5点）

- [x] 345 + 278 の答えは、600より大きい。
- [ ] 902 − 456 の答えは、500より大きい。
- [x] 124 × 3 と 3 × 124 は、同じ答えになる。
:::

:::exercise{type=open area=lines lines=2}
354円のノートと278円のペンを買いました。あわせて何円ですか。（式5点・答え5点）

:::solution
式　354 + 278 = 632　　答え　632円
:::
:::

:::exercise{type=open area=lines lines=2}
456ページの本を、きのうまでに278ページ読みました。のこりは何ページですか。（式5点・答え5点）

:::solution
式　456 − 278 = 178　　答え　178ページ
:::
:::

# 春のことば {kicker="こくご　12" pic="kitsune"}

:::paragraphs{style="namae"}
名前:chip[　]{style="sen"}　　:chip[　]{style="waku"}点
:::

:::exercise
□に漢字を書きましょう。（1つ5点）

:::columns{count=3}
はる

[[春]]

はな

[[花]]

かぜ

[[風]]

そら

[[空]]

あさ

[[朝]]

ひる

[[昼]]
:::
:::

:::exercise
線を引いた漢字の読みがなを書きましょう。（1つ5点）

1. :sideline[春風]がふく。（[[はるかぜ]]）
2. :sideline[朝日]がのぼる。（[[あさひ]]）
3. 花の:sideline[色]がきれいだ。（[[いろ]]）
:::

:::exercise
文に合うことばを、○でかこみましょう。（1つ5点）

1. 春の風がふいて、さくらの花が [[(ちりました) | のぼりました]]。
2. 朝、つばめが南の国から [[(やってきた) | ねむっていた]]。
:::

:::exercise{columns=1}
ことばのいみに合うものを、えらびましょう。（10点）

「うららか」とは、どんなようすですか。

- [ ] 雨がはげしくふるようす
- [x] 空が晴れて、日の光がやわらかいようす
- [ ] 風がつめたくふくようす
:::

:::paragraphs{style="colophon"}
書体：Klee One、Zen Maru Gothic（SIL OFL）　絵：拡散モデルで生成　問題：本書のための書き下ろし（CC BY 4.0）
:::
`; // content.ja.md: the さんすう page, then the こくご page

// ─── 3 · Fonts ──────────────────────────────────────────────────────────────
const FONTS = {
  'Klee One': ['400', '600'], // 教科書体: the text and the numbers to copy
  'Zen Maru Gothic': ['400', '700'], // labels, instructions, titles, the answers
};

// ─── 4 · Build & show ───────────────────────────────────────────────────────
// Each face loads the files of the characters it sets (gotcha: cjk-fonts-slices); the
// vertical page also needs each face's upright punctuation.
await loadFonts(FONTS, markdown);
await loadCjkFonts(FONTS, markdown, { vertical: true });
const resources = [];
for (const id of ['tanuki', 'kitsune']) {
  await loadImage(`${id}-600.jpg`, asset(id === 'tanuki' ? 'tanuki-600.jpg' : 'kitsune-600.jpg'));
  resources.push({ id, typeId: 'figure', kind: 'bitmap', createdAt: 0, updatedAt: 0,
    bitmap: { fileId: `${id}-600.jpg`, format: 'jpeg', width: 600, height: 600 } });
}
// #region two-books: one drill across, one in columns, with the same styles
// Two drill books of one series: arithmetic across, bound on the left; kanji in columns,
// bound on the right (vertical text binds there by itself).
const [sansu, kokugo] = markdown.split(/(?=^# 春のことば)/m);
const build = (text) => withLoadedFonts(() => buildDocument({ markdown: text, resources },
  config()), { ...kitFonts(FONTS), text: markdown });
const across = await build(sansu);
// 国語 is set in columns, top to bottom, right to left: the same design, turned.
writingMode = 'vertical-rl';
const docs = [across, await build(kokugo)];
// #endregion
showBook(docs, { title: t({ ja: '答えがさかさまのドリル', en: 'A Japanese drill, answers upside down',
  es: 'Un cuaderno japonés con las soluciones del revés' }) });
offerPdf(() => renderToPdf(docs, { fontProvider: cjkPdfProvider, resourceBytes: imageBytes }),
  `${RECIPE}.pdf`);

// ─── Kit ── helpers shared by every Cookbook recipe · postext.dev/cookbook ─────

// ─── Kit · core v1 ── the same in every recipe · postext.dev/cookbook
function mm(value) { return { value, unit: 'mm' }; }
function pt(value) { return { value, unit: 'pt' }; }
function em(value) { return { value, unit: 'em' }; }
/** The sample language's string: t({ en: 'Figure', es: 'Figura' }). */
function t(strings) { return strings[LANG] ?? Object.values(strings)[0]; }
/** A file in this recipe's assets folder, served from the Postext repo by jsDelivr. */
function asset(file) { return `https://cdn.jsdelivr.net/gh/drnachio/postext@main/cookbook/${RECIPE}/assets/${file}`; }

// ─── Kit · fonts v3 ── the same in every recipe · postext.dev/cookbook
// Postext loads the faces a config asks for before layout and asks the kit
// for Fontsource's files, the ones the PDF embeds too.

/** buildDocumentWithFonts' options: the resolver, and FONTS' faces loaded
 *  with the config's. FONTS = { 'Family Name': ['400', '400i', '700'] }. */
function kitFonts(FONTS = {}) {
  const faces = Object.entries(FONTS).flatMap(([family, specs]) => specs.map((spec) =>
    ({ family, weight: parseInt(spec, 10), style: spec.endsWith('i') ? 'italic' : 'normal' })));
  return { resolve: fontsourceResolver, faces };
}

/** A face's files with their ranges: latin, then latin-ext and greek when
 *  `text` needs them (kitSubsetsFor). Null for a face Fontsource lacks. */
async function fontsourceResolver(family, weight, style, { text = '' } = {}) {
  const id = fontsourceId(family);
  const meta = await fontsourceMeta(family);
  if (meta && !(await fontsourceWeights(family, style)).includes(weight)) return null;
  kitStatus('Loading fonts…');
  const at = await fontsourceAt(id);
  return ['latin', ...kitSubsetsFor(text, meta)].map((subset) => ({
    source: `${at}files/${id}-${subset}-${weight}-${style}.woff2`,
    unicodeRange: kitRanges()[subset],
  }));
}

/** Each file's unicode-range (a function: the kit runs after the pen's code). */
function kitRanges() {
  return {
    latin: 'U+0000-00FF,U+0131,U+0152-0153,U+02BB-02BC,U+02C6,U+02DA,U+02DC,U+0304,U+0308,U+0329,'
      + 'U+2000-206F,U+20AC,U+2122,U+2191,U+2193,U+2212,U+2215,U+FEFF,U+FFFD',
    'latin-ext': 'U+0100-02BA,U+02BD-02C5,U+02C7-02CC,U+02CE-02D7,U+02DD-02FF,U+0304,U+0308,U+0329,'
      + 'U+1D00-1DBF,U+1E00-1E9F,U+1EF2-1EFF,U+2020,U+20A0-20AB,U+20AD-20C0,U+2113,U+2C60-2C7F,U+A720-A7FF',
    greek: 'U+0370-03FF',
  };
}

/** For the cjk, arabic and comics blocks: loads `faces` (as FONTS) for the
 *  sample `text`; `optional` skips a face Fontsource lacks. Files are added in
 *  the order asked, the last winning a shared character. Resolves to the count. */
async function loadFonts(faces, text = '', { optional = false } = {}) {
  kitStatus('Loading fonts…');
  const ranges = kitRanges();
  const jobs = [];
  for (const [family, specs] of Object.entries(faces)) {
    const id = fontsourceId(family);
    const todo = [...new Set(specs)].map((spec) => [parseInt(spec, 10), spec.endsWith('i') ? 'italic' : 'normal'])
      .filter(([weight, style]) => !hasFace(family, weight, style)); // before any await
    const at = fontsourceAt(id);
    const meta = optional || /[^\0-ÿ]/u.test(text) ? await fontsourceMeta(family) : null;
    const subsets = ['latin', ...kitSubsetsFor(text, meta)];
    for (const [weight, style] of todo) {
      if (optional && !(meta && (await fontsourceWeights(family, style)).includes(weight))) continue;
      for (const subset of subsets) {
        const url = `${await at}files/${id}-${subset}-${weight}-${style}.woff2`;
        const face = new FontFace(family, `url(${url}) format('woff2')`,
          { weight: String(weight), style, unicodeRange: ranges[subset] });
        jobs.push(face.load().catch(() => {
          if (subset === 'latin' && !optional) throw new Error(`Fontsource has no ${family} ${weight} ${style}`);
        }));
      }
    }
  }
  const ready = await Promise.all(jobs).catch((error) => { kitFail(error); throw error; });
  return ready.filter((face) => face && document.fonts.add(face)).length;
}

/** A loaded FontFace covers this face (fonts.check() says yes to any family). */
function hasFace(family, weight, style) {
  for (const face of document.fonts) {
    if (face.status !== 'loaded' || face.style !== style) continue;
    if (face.family.replace(/^["']|["']$/g, '') !== family) continue;
    const [low, high = low] = face.weight.split(' ').map(Number);
    if (weight >= low && weight <= high) return true;
  }
  return false;
}

/** The files beyond latin `text` needs that `meta`'s family ships. */
function kitSubsetsFor(text, meta) {
  return [[/[Ā-˿ᴀ-ᶿḀ-ỿ†ℓⱠ-Ɀ꜠-ꟿ]/u, 'latin-ext'], [/[Ͱ-Ͽ]/u, 'greek']]
    .filter(([re, x]) => re.test(text) && meta?.subsets?.includes(x)).map(([, x]) => x);
}

/** Fontsource's id for a family: 'Source Serif 4' → 'source-serif-4'. */
function fontsourceId(family) { return family.toLowerCase().replace(/\s+/g, '-'); }

/** A package's folder at the one version @5 names now (#766). */
function fontsourceAt(id, u = `https://cdn.jsdelivr.net/npm/@fontsource/${id}@`) {
  return (fontsourceAt.c ??= {})[id] ??= fetch(u + '5/package.json').then((r) => r.json())
    .then((p) => p.version || 5, () => 5).then((v) => `${u}${v}/`);
}

/** The family's Fontsource metadata (weights, styles, subsets), or null. */
function fontsourceMeta(family, id = fontsourceId(family)) {
  return (fontsourceMeta.c ??= {})[id] ??= fetch(`https://api.fontsource.org/v1/fonts/${id}`)
    .then((res) => (res.ok ? res.json() : null), () => null);
}

/** The weights the package ships in `style`: the API pairs none (no Libre
 *  Caslon 700 italic file), so italics are read from latin-italic.css. */
function fontsourceWeights(family, style, id = fontsourceId(family)) {
  return (fontsourceWeights.c ??= {})[id + style] ??= fontsourceMeta(family).then(async (m) => {
    if (!m?.styles.includes(style)) return m ? [] : [400, 700];
    const css = style === 'italic' ? await fetch(`${await fontsourceAt(id)}latin-italic.css`).then((r) => (r.ok ? r.text() : ''), () => '') : '';
    const w = [...css.matchAll(/weight: (\d+)/g)].map((x) => +x[1]);
    return w.length ? w : m.weights;
  });
}

// ─── Kit · viewer v2 ── the same in every recipe · postext.dev/cookbook
/** The pages as spreads on a dark desk, page 1 alone, then verso | recto,
 *  each painted when it scrolls near. Other options go to renderPageToCanvas. */
function showPages(docs, { title, width = 460, ...render } = {}) {
  const root = viewer(title);
  const pages = [docs].flat().flatMap((doc) =>
    doc.pages.map((page) => ({ doc, page, n: (doc.pageIndexOffset ?? 0) + page.index })));
  const spreads = [];
  let verso = null;
  for (const p of pages) {
    if (p.n % 2 === 1) { if (verso) spreads.push([verso, null]); verso = p; }
    else { spreads.push([verso, p]); verso = null; }
  }
  if (verso) spreads.push([verso, null]);
  const density = Math.min(window.devicePixelRatio || 1, 2);
  showPages.painter?.disconnect();
  const painter = new IntersectionObserver((entries) => {
    for (const { isIntersecting, target } of entries) {
      if (!isIntersecting) continue;
      painter.unobserve(target);
      const { doc, page } = target.postext;
      renderPageToCanvas(page, doc, target, { ...render, scale: (width * density) / page.width });
    }
  }, { rootMargin: '800px' });
  showPages.painter = painter;
  root.replaceChildren(...spreads.map((pair) => {
    const spread = document.createElement('div');
    spread.className = 'pt-spread';
    for (const p of pair) {
      const figure = document.createElement('figure');
      if (p) {
        const label = p.page.pageLabel || String(p.n + 1);
        const canvas = document.createElement('canvas');
        canvas.postext = p;
        canvas.style.aspectRatio = `${p.page.width} / ${p.page.height}`;
        canvas.setAttribute('role', 'img');
        canvas.setAttribute('aria-label', `Page ${label}`);
        const folio = document.createElement('figcaption');
        folio.textContent = label;
        figure.append(canvas, folio);
        painter.observe(canvas);
      } else figure.className = 'pt-blank';
      spread.append(figure);
    }
    return spread;
  }));
  kitStatus(`${pages.length} ${pages.length === 1 ? 'page' : 'pages'}`);
  document.documentElement.dataset.postext = 'ready';
  return pages.length;
}

/** The desk, the bar and the error reporting, created once. */
function viewer(title) {
  if (!document.getElementById('pt-kit')) {
    document.head.insertAdjacentHTML('beforeend', `<style id="pt-kit">
      :root { color-scheme: dark; }
      body { margin: 0; background: #0e1014; color: #b9bcc4; font: 13px/1.45 system-ui, sans-serif; }
      #pt-bar { position: sticky; top: 0; z-index: 1; display: flex; flex-wrap: wrap; align-items: center;
        gap: 6px 16px; padding: 10px 16px; background: rgb(14 16 20 / .92); backdrop-filter: blur(6px);
        border-bottom: 1px solid #23262d; }
      #pt-bar strong { color: #f4f1ea; font-weight: 600; }
      #pt-actions { display: flex; gap: 12px; margin-left: auto; }
      #pt-actions a, #pt-actions button { color: #d8a21a; font: inherit; background: none; border: 0; padding: 0; cursor: pointer; }
      #pages { display: grid; justify-items: center; gap: 48px; padding: 32px 16px 72px; }
      .pt-spread { display: flex; }
      .pt-spread figure { margin: 0; width: min(460px, 44vw); }
      .pt-spread canvas { display: block; width: 100%; background: #fff;
        box-shadow: 0 1px 2px rgb(0 0 0 / .5), 0 22px 44px -16px rgb(0 0 0 / .8); }
      .pt-spread figure:first-child canvas { box-shadow: inset -14px 0 14px -14px rgb(0 0 0 / .18), 0 1px 2px rgb(0 0 0 / .5), 0 22px 44px -16px rgb(0 0 0 / .8); }
      .pt-spread figcaption { margin-top: 10px; text-align: center; font: 600 10px/1 system-ui, sans-serif;
        letter-spacing: .18em; text-transform: uppercase; color: #6c7079; }
      .pt-blank { visibility: hidden; }
      @media (max-width: 760px) {
        .pt-spread { flex-direction: column; gap: 32px; }
        .pt-spread figure { width: min(460px, 92vw); }
        .pt-blank { display: none; }
      }
    </style>`);
    document.body.insertAdjacentHTML('afterbegin',
      '<header id="pt-bar"><strong id="pt-title"></strong><span id="pt-status" role="status"></span><span id="pt-actions"></span></header>');
    document.getElementById('pt-title').textContent = document.title || 'Postext';
    addEventListener('error', (event) => kitFail(event.error ?? event.message));
    addEventListener('unhandledrejection', (event) => kitFail(event.reason));
  }
  if (title) document.getElementById('pt-title').textContent = title;
  return document.getElementById('pages')
    ?? document.body.appendChild(Object.assign(document.createElement('main'), { id: 'pages' }));
}

function kitStatus(text) {
  viewer();
  document.getElementById('pt-status').textContent = text;
}

function kitFail(error) {
  document.documentElement.dataset.postext = 'error';
  kitStatus(`Error: ${error?.message ?? error}`);
}

// ─── Kit · pdf v3 ── the same in every recipe that exports a PDF
/** The Fontsource files the screen used, as TrueType, with their range and
 *  place: the nearest weight the family ships in that style, upright with no italic;
 *  latin, then what its letters need (kitSubsetsFor). */
async function fontsourceProvider(family, weight, style, request) {
  const id = fontsourceId(family);
  const meta = await fontsourceMeta(family);
  const s = style === 'italic' && meta && !meta.styles.includes('italic') ? 'normal' : style;
  const shipped = meta ? await fontsourceWeights(family, s) : [];
  const weights = shipped.length ? shipped : [400, 700];
  const w = weights.reduce((a, b) => (Math.abs(b - weight) < Math.abs(a - weight) ? b : a));
  const text = String.fromCodePoint(...(request?.codePoints ?? []));
  const files = await Promise.all(['latin', ...kitSubsetsFor(text, meta)].map(async (subset, order) => {
    const res = await fetch(`${await fontsourceAt(id)}files/${id}-${subset}-${w}-${s}.woff2`);
    if (!res.ok) throw new Error(`Fontsource has no ${family} ${w} ${s} ${subset}`);
    return Object.assign(await decompressWoff2(new Uint8Array(await res.arrayBuffer())),
      { unicodeRange: kitRanges()[subset], order });
  }));
  return files.length === 1 ? files[0] : files;
}

/** A "Build the PDF" button; then "Open the PDF" (a new tab: CodePen's frame
 *  shows no PDFs) and a download link. */
function offerPdf(makePdf, filename) {
  viewer();
  const button = Object.assign(document.createElement('button'), { type: 'button', textContent: 'Build the PDF' });
  button.dataset.postextPdf = filename;
  button.addEventListener('click', async () => {
    button.disabled = true;
    button.textContent = 'Building the PDF…';
    try {
      const bytes = await makePdf();
      const url = URL.createObjectURL(new Blob([bytes], { type: 'application/pdf' }));
      const size = `${Math.max(1, Math.round(bytes.length / 1024))} KB`;
      button.replaceWith(
        Object.assign(document.createElement('a'), { href: url, target: '_blank', rel: 'noopener', textContent: 'Open the PDF ↗' }),
        Object.assign(document.createElement('a'), { href: url, download: filename, textContent: `Download ${filename} · ${size}` }));
    } catch (error) {
      button.disabled = false;
      button.textContent = 'Build the PDF';
      kitFail(error);
    }
  });
  document.getElementById('pt-actions').append(button);
}

// ─── Kit · images v3 ── recipes with pictures · postext.dev/cookbook
/** Registers a photo or PNG for the canvas and keeps its bytes for the PDF.
 *  fetch → ImageBitmap never taints the canvas (a plain cross-origin <img> would). */
async function loadImage(fileId, url) {
  const res = await fetch(url);
  if (!res.ok) throw new Error(`Image not found (${res.status}): ${url}`);
  const bytes = new Uint8Array(await res.arrayBuffer());
  registerResourceImage(fileId, await createImageBitmap(new Blob([bytes])));
  (loadImage.bytes ??= new Map()).set(fileId, bytes);
}

/** Registers SVG markup as a vector image, its fonts inside (inlineSvgFonts, ≥ 1.25).
 *  `options` go to registerResourceImage: { singleInk: true } tints it on the canvas. */
async function loadSvg(fileId, svg, options) {
  if (typeof inlineSvgFonts === 'function') svg = await inlineSvgFonts(svg, svgFaces);
  const img = new Image();
  img.src = `data:image/svg+xml;charset=utf-8,${encodeURIComponent(svg)}`;
  await img.decode();
  registerResourceImage(fileId, img, options);
  (loadImage.bytes ??= new Map()).set(fileId, new TextEncoder().encode(svg));
}

/** A face's Fontsource files: nearest weight; latin + what the SVG sets. */
async function svgFaces(family, weight, style, { codePoints = [] } = {}) {
  const [id, m] = [fontsourceId(family), await fontsourceMeta(family)];
  const w = m?.weights.reduce((a, b) => (Math.abs(b - weight) < Math.abs(a - weight) ? b : a)) ?? weight;
  const s = m?.styles.includes(style) === false ? 'normal' : style;
  return Promise.all(['latin', ...kitSubsetsFor(String.fromCodePoint(...codePoints), m)].map(async (x) => new Uint8Array(
    await (await fetch(`${await fontsourceAt(id)}files/${id}-${x}-${w}-${s}.woff2`)).arrayBuffer())));
}

/** renderToPdf({ resourceBytes: imageBytes }) */
function imageBytes(fileId) { return loadImage.bytes?.get(fileId); }

/** renderToHtml({ resourceImageUrl: imageUrl }) */
function imageUrl(fileId) {
  const bytes = imageBytes(fileId);
  if (!bytes) return undefined;
  imageUrl.urls ??= new Map();
  if (!imageUrl.urls.has(fileId)) {
    const type = /\.svg$/i.test(fileId) ? 'image/svg+xml' : /\.png$/i.test(fileId) ? 'image/png' : 'image/jpeg';
    imageUrl.urls.set(fileId, URL.createObjectURL(new Blob([bytes], { type })));
  }
  return imageUrl.urls.get(fileId);
}

// ─── Kit · cjk v2 ── Chinese, Japanese and Korean books · postext.dev/cookbook
// Fontsource ships a CJK family as about a hundred files per weight, each
// declared in its stylesheet with the unicode-range it covers. The screen
// loads the files the sample touches; the PDF gets the same files for the
// characters its pages set in each face, and embeds each as a subset.
// A book bound on the right (vertical text) is shown with its spreads
// mirrored: page 1 alone on the left of the spine, then [3 | 2].

/** The files of a Fontsource face, read from its stylesheet: { url, range,
 *  ranges }, the last declared first (the order the browser tries them in). */
function cjkSlices(family, weight, style) {
  cjkSlices.cache ??= new Map();
  const id = fontsourceId(family);
  const css = `${id}/${weight}${style === 'italic' ? '-italic' : ''}.css`;
  if (!cjkSlices.cache.has(css)) {
    let at;
    cjkSlices.cache.set(css, fontsourceAt(id).then((a) => fetch(at = a + css.slice(id.length + 1)))
      .then((res) => {
        if (!res.ok) throw new Error(`Fontsource has no ${family} ${weight} ${style} (${res.status})`);
        return res.text();
      })
      .then((text) => [...text.matchAll(/@font-face\s*{([^}]*)}/g)].map(([, rule]) => {
        const range = /unicode-range:\s*([^;]+);/.exec(rule)?.[1].trim() ?? 'U+0-10FFFF';
        const ranges = range.split(',').map((part) => {
          const [lo, hi = lo] = part.trim().slice(2).split('-');
          return [parseInt(lo, 16), parseInt(hi, 16)];
        });
        return { url: new URL(/url\(([^)]+?\.woff2)\)/.exec(rule)[1], at).href, range, ranges };
      }).reverse()));
  }
  return cjkSlices.cache.get(css);
}

/** The file of `slices` the screen sets code point `cp` in, if any: the
 *  last one loadCjkFonts adds whose range holds it. A numbered file that
 *  repeats a letter of latin is added after latin, and wins it. */
function cjkSliceFor(slices, cp) {
  const holds = (slice) => slice.ranges.some(([lo, hi]) => cp >= lo && cp <= hi);
  return slices.reduce((last, slice) => (holds(slice) ? slice : last), undefined);
}

/** Whether Fontsource serves `family` as a Chinese, Japanese or Korean
 *  family (its subsets name the script). Fails when the API does not
 *  answer: a CJK face taken for a Latin one would paint in a system face. */
async function isCjkFamily(family) {
  const meta = await fontsourceMeta(family);
  if (!meta) throw new Error(`api.fontsource.org did not describe ${family}: reload to try again`);
  return !!meta.subsets?.some((subset) => /^(chinese|japanese|korean)/.test(subset));
}

/** faces = { 'Noto Serif TC': ['400', '700'] }, as for loadFonts: the
 *  whole FONTS object may be passed, its other families are left to
 *  loadFonts. Adds one FontFace per file of each CJK face with its
 *  unicodeRange, then loads the files `text` touches. `text` is what the
 *  faces set: the sample for the text face; a book in several voices calls
 *  it once per voice (loadCjkFonts({ 'LXGW WenKai TC': ['400'] }, quotes)),
 *  so the heading and quotation faces fetch and check only their own
 *  characters. Fails when a character of `text` is in no file of a face.
 *  List every weight the pages use: a weight left to the engine's later round
 *  gets the latin file only. With { vertical: true } it also loads each
 *  family's vertical forms (brackets, quotes, pause marks) for the canvas,
 *  which needs loadVerticalAlternates imported from postext. Resolves to
 *  the number of files loaded. */
async function loadCjkFonts(faces, text, { vertical = false } = {}) {
  kitStatus('Loading fonts…');
  let loaded = 0;
  try {
    if (vertical && typeof loadVerticalAlternates !== 'function') {
      throw new Error('loadCjkFonts(…, { vertical: true }) needs loadVerticalAlternates imported from postext');
    }
    for (const [family, specs] of Object.entries(faces)) {
      if (!(await isCjkFamily(family))) continue;
      const twin = [];
      for (const spec of new Set(specs)) {
        const weight = parseInt(spec, 10);
        const style = spec.endsWith('i') ? 'italic' : 'normal';
        const slices = await cjkSlices(family, weight, style);
        const missing = [...new Set(text)].filter((ch) => /\S/.test(ch) && !cjkSliceFor(slices, ch.codePointAt(0)));
        if (missing.length) {
          throw new Error(`${family} ${spec} has no file for ${missing.slice(0, 12).join(' ')}: `
            + `give each face the text it sets (loadCjkFonts({ '${family}': ['${spec}'] }, text))`);
        }
        for (const slice of slices) {
          document.fonts.add(new FontFace(family, `url(${slice.url}) format('woff2')`,
            { weight: String(weight), style, unicodeRange: slice.range }));
          twin.push({ source: slice.url, weight: String(weight), style, unicodeRange: slice.range });
        }
        const font = `${style === 'italic' ? 'italic ' : ''}${weight} 16px "${family}"`;
        loaded += (await document.fonts.load(font, text)).length;
        if (!document.fonts.check(font, text)) throw new Error(`${family} ${spec} did not load for the sample`);
      }
      // The same files under a twin name with the `vert` feature on: the
      // canvas paints the punctuation of vertical lines with it.
      if (vertical && twin.length) await loadVerticalAlternates(family, twin);
    }
  } catch (error) {
    kitFail(error);
    throw error;
  }
  return loaded;
}

/** The PDF font provider for recipes with CJK faces: a family whose
 *  Fontsource subsets are Chinese, Japanese or Korean gets the files the
 *  screen set its pages' characters in (`request.codePoints`), each marked
 *  with its unicode-range and its place in the order loadCjkFonts added
 *  them: postext-pdf sets a character two files hold in the one added
 *  last, as the browser does. Any other family gets the latin file
 *  fontsourceProvider fetches (the "pdf" block) and, when the face sets
 *  letters only latin-ext has, that file too. */
async function cjkPdfProvider(family, weight, style, request) {
  if (!(await isCjkFamily(family))) return cjkLatinPdfFiles(family, weight, style, request);
  const meta = await fontsourceMeta(family);
  const weights = meta.weights?.length ? meta.weights : [400, 700];
  const w = weights.reduce((a, b) => (Math.abs(b - weight) < Math.abs(a - weight) ? b : a));
  const s = style === 'italic' && !meta.styles.includes('italic') ? 'normal' : style;
  const slices = await cjkSlices(family, w, s);
  const picked = new Set();
  for (const cp of request?.codePoints ?? []) {
    const slice = cjkSliceFor(slices, cp);
    if (slice) picked.add(slice);
  }
  if (!picked.size) picked.add(slices[0]);
  return Promise.all(slices.map(async (slice, order) => {
    if (!picked.has(slice)) return null;
    const res = await fetch(slice.url);
    if (!res.ok) throw new Error(`Fontsource file ${slice.url} (${res.status})`);
    const bytes = await decompressWoff2(new Uint8Array(await res.arrayBuffer()));
    return Object.assign(bytes, { unicodeRange: slice.range, order });
  })).then((files) => files.filter(Boolean));
}

/** A Latin family set next to the CJK faces: its latin file, then its
 *  latin-ext file when the face sets letters only latin-ext has (ō ū in
 *  Hepburn rōmaji, ǎ in pinyin), the file loadFonts adds on screen for
 *  them, each marked with its unicode-range and its place in that order:
 *  the PDF sets a character in the file the browser took it from. A face
 *  Fontsource ships without latin-ext, or whose file does not come, gets
 *  latin alone, and the PDF names the letters it lacks. */
async function cjkLatinPdfFiles(family, weight, style, request) {
  const meta = await fontsourceMeta(family);
  const beyond = [...(request?.codePoints ?? [])].some(cjkLatinExtOnly);
  if (!beyond || !meta?.subsets?.includes('latin-ext')) return fontsourceProvider(family, weight, style);
  const weights = meta.weights?.length ? meta.weights : [400, 700];
  const w = weights.reduce((a, b) => (Math.abs(b - weight) < Math.abs(a - weight) ? b : a));
  const s = style === 'italic' && !meta.styles.includes('italic') ? 'normal' : style;
  const id = fontsourceId(family);
  const url = `${await fontsourceAt(id)}files/${id}-latin-ext-${w}-${s}.woff2`;
  const [latin, ext] = await Promise.all([fontsourceProvider(family, weight, style), fetch(url)
    .then(async (res) => (res.ok ? decompressWoff2(new Uint8Array(await res.arrayBuffer())) : null), () => null)]);
  const ranges = kitRanges();
  return ext ? [Object.assign(latin, { unicodeRange: ranges.latin, order: 0 }),
    Object.assign(ext, { unicodeRange: ranges['latin-ext'], order: 1 })] : latin;
}

/** Whether code point `cp` is in Fontsource's latin-ext file and not in
 *  its latin file: Latin Extended-A and -B, IPA, the spacing modifiers and
 *  Latin Extended Additional (loadFonts's test for latin-ext), less the
 *  few latin holds too (ı Œ œ ʻ ʼ ˆ ˚ ˜). */
function cjkLatinExtOnly(cp) {
  if (!((cp >= 0x100 && cp <= 0x2ff) || (cp >= 0x1e00 && cp <= 0x1eff))) return false;
  return ![0x131, 0x152, 0x153, 0x2bb, 0x2bc, 0x2c6, 0x2da, 0x2dc].includes(cp);
}

/** showPages for a book bound on either edge. A right-bound book (the
 *  document says so: doc.binding is 'right' for page.binding 'right' and
 *  for vertical text) lies on the desk as it opens: page 1 alone on the
 *  left of the spine, then [3 | 2], the spine shade on each page's inner
 *  edge. `binding` ('left' | 'right') overrides the document's. */
function showBook(docs, { binding, ...options } = {}) {
  const count = showPages(docs, options);
  const right = (binding ?? [docs].flat()[0]?.binding) === 'right';
  if (!document.getElementById('pt-kit-cjk')) {
    // The pages keep direction ltr: a canvas draws text in the direction its
    // element inherits, and under rtl each run would end where the engine
    // starts it, its brackets mirrored.
    document.head.insertAdjacentHTML('beforeend', `<style id="pt-kit-cjk">
      .pt-spread[dir="rtl"] canvas { direction: ltr; }
      .pt-spread[dir="rtl"] figure:first-child canvas { box-shadow: inset 14px 0 14px -14px rgb(0 0 0 / .18),
        0 1px 2px rgb(0 0 0 / .5), 0 22px 44px -16px rgb(0 0 0 / .8); }
    </style>`);
  }
  // Each pair stays [verso, recto] in the page; right to left, the verso
  // sits on the right. Phones stack the pages in reading order either way.
  for (const spread of document.querySelectorAll('#pages > .pt-spread')) spread.dir = right ? 'rtl' : 'ltr';
  document.getElementById('pages').dataset.binding = right ? 'right' : 'left';
  return count;
}

// ─── /Kit ───────────────────────────────────────────────────────────────────────
```

## アレンジ

### こたえを最後にまとめる

別冊解答がつくドリルなら、こたえは問題のページに入れません。`chapterEnd` にすると、最後の問題のあとにまとめて載ります。

```diff
-  solutions: { placement: 'inverted', box: 'kotae' },
+  solutions: { placement: 'chapterEnd', box: 'kotae' },
```

### パズルのページを組む

[パズルのページ](https://postext.dev/ja/cookbook/puzzle-page-upside-down-answers.md)も、同じやり方でこたえを逆さまにして、2段のカードに載せています。

## よくあるつまずき

- **中国語の書体はcjkブロックを通じてスライス単位で読み込む.** Fontsourceは中国語、日本語、韓国語のファミリーを、ウェイトごとに約100個のファイルとして配信し、各ファイルが文字の範囲を受け持ちます。loadFontsが取得するのはlatinファイルだけなので、画面では漢字がシステムの書体で出て計測が狂い、fontsourceProviderはPDFにそのlatinファイルを渡すため、漢字が空の四角で印字されます。キットのcjkブロックを挙げ、loadFontsのあとにloadCjkFonts(FONTS, markdown)を呼び（本で複数のCJK書体を使うときは、それぞれの書体で組むテキストを渡して書体ごとに1回）、renderToPdfにfontProvider: cjkPdfProviderを渡してください。どちらもテキストの文字を含むファイルを取得します。
- **日本語のテキストのタグは'ja'。zh-HansやLANGにしない.** レシピの版はenとesですが、日本語のサンプルはどちらの版でも日本語です。`locale: LANG`では英語やスペイン語とタグ付けされ、中国語のタグでは中国語の規則で組まれます（開明式の約物、小書きの仮名が行頭に来てもよい、図の代わりに图、PDFでは中国の字形）。postext 1.30以降、このタグはテキストを組む言語（計測、描画、埋め込みに使う言語）でもあるので、'ja'以外のタグでは日本語の字形ではなく別の字形（中国語のタグでは中国の字形）になり、改行の位置も変わります。'ja'と書いてください。日本の地域（JLReqの改行と約物、ゴマの圏点、ルビの間隔、図と表の表示名）が選ばれ、ハイフネーションが切られます。リントは、zhやkoのタグで仮名を含むテキストをエラーにします。

- 今のところ、空欄の上に読みがなは置けません。`[[…]]` の中のルビは、隠したこたえの一部になります。漢字の書き取りの問題では、読みを1行に置いてそのあとに□を続け、`:::columns` のグループで1列に3つずつ並べます。縦組みのページでは、ふりがなと同じように、読みが□の横に立ちます。
- Klee One には400と600しかありません。`boldFontWeight: 600` にしておくと、小問と大問の番号も含めて、太字はすべて実在するウェイトで組まれます。

## クレジット

- レシピ: Ignacio Ferro ([@drnachio](https://github.com/drnachio))
- 画像: A young tanuki in a yellow school hat holding a big pencil.: Generated With Diffusion Models, オリジナル
- 画像: A fox cub in a red scarf reading a book.: Generated With Diffusion Models, オリジナル
- 書体: Klee One (OFL-1.1), Zen Maru Gothic (OFL-1.1)
- コード: MIT · サンプルの内容: CC-BY-4.0

## 関連レシピ

- [No. 174 · 答えを逆さに刷ったパズルページ](https://postext.dev/ja/cookbook/puzzle-page-upside-down-answers.md): 子ども向け雑誌のパズルページです。クロスワード、ワードサーチ、なぞなぞ、話の並べ替えなどをカードに載せ、答えはそれぞれ逆さに刷ります。 · 難易度 2 (中級) · 雑誌とジン, ワークブックと練習問題
- [No. 124 · すべての漢字にふりがなを付けた国語の教科書](https://postext.dev/ja/cookbook/jukugo-furigana-textbook.md): 新美南吉『ごんぎつね』を教科書のページに。モノルビ、グループルビ、熟語ルビを1:2:1で配置し、かなには掛けても漢字には掛けません。 · 難易度 2 (中級) · 教科書
- [No. 169 · 1枚のプリントを10の国の学校の流儀で](https://postext.dev/ja/cookbook/school-traditions-worksheet.md): 同じ7つの :::exercise を10の言語で組みます。各版は、その国の教科書が問題を組むやり方にならった問題スタイルで印刷します。 · 難易度 2 (中級) · ワークブックと練習問題, 教科書