diff --git a/README.md b/README.md
index 0c6d075..d336eb6 100644
--- a/README.md
+++ b/README.md
@@ -165,6 +165,34 @@ portal and console each pin its SHA-256. `scripts/check-styles.mjs` holds the da
 prints that hash. **A change here must be followed by the portal and the console taking the file
 again and moving their pins to the new hash.** Until they do, their checks fail.
 
+## Type
+
+`src/data/type.ts` is the source for the house font set and the twelve pairings a client picks
+from. It holds sixteen families: fifteen Fontsource packages and the device's own sans. Each
+family records its board class (a `FontKey` from styles.ts), package, licence, designer, axes,
+the weights the pairings use, a metric-matched fallback with its `size-adjust` and overrides, and
+the kilobytes of its Latin woff2. Each pairing records a heading, a body and an optional label
+family, a feel, recommended heading and body settings, what it suits, and the style boards it
+serves. `familyFor(key)` gives the family a board class renders in. It is plain data with no
+imports, so any app can copy it. **No font file is committed here.** A site installs the
+package, imports the Latin subset and serves it from its own origin.
+
+The rules are strict. Only SIL OFL 1.1 and Apache 2.0 are allowed, because both let the files be
+redistributed and self-hosted. A pairing's families weigh at most 120 KB together. "System"
+costs nothing and stays on the list. A pairing serves a board only when its families match the
+board's heading and body classes, and its label class when the board has one, so the board's
+`type.note` stays true. `kb` and `metrics` were measured from the Fontsource 5.3.0 files with
+Capsize. The header of `type.ts` says how.
+
+It is consumed by:
+
+- **SuperheroPortal**, `src/brand/type.data.ts`: the brand guide's typography and hearts.
+- **superherotech.ai**, which vendors it for the public `/type/` page and to render `/styles/`.
+
+The pin rule is the same as for style boards. Only the file header may differ between copies, each
+copy pins the SHA-256 of the body, and `scripts/check-type.mjs` prints it. **A change here must
+be followed by the copies taking the file again and moving their pins to the new hash.**
+
 ## Licence
 
 MIT, Ecropolis LLC. Elements are copied into client sites; see `LICENSE`.
diff --git a/package.json b/package.json
index 9eabc47..4529f8c 100644
--- a/package.json
+++ b/package.json
@@ -12,7 +12,7 @@
     "preview": "astro preview",
     "astro": "astro",
     "build:icon-data": "node scripts/build-icon-data.mjs",
-    "check": "node --experimental-strip-types --disable-warning=ExperimentalWarning scripts/check-catalog.mjs && node --disable-warning=ExperimentalWarning scripts/check-business-hours.mjs && node scripts/check-news-ticker.mjs && node --disable-warning=ExperimentalWarning scripts/check-flip-box.mjs && node scripts/check-social-grid.mjs && node --experimental-strip-types --disable-warning=ExperimentalWarning scripts/check-four.mjs && node --disable-warning=ExperimentalWarning scripts/check-video-player.mjs && node scripts/check-cookie-consent.mjs && node --experimental-strip-types --disable-warning=ExperimentalWarning scripts/check-icon.mjs && node --experimental-strip-types --disable-warning=ExperimentalWarning scripts/check-animated-background.mjs && node --disable-warning=ExperimentalWarning scripts/check-modal-and-bar.mjs && node --disable-warning=ExperimentalWarning scripts/check-reveal-cards.mjs && node --disable-warning=ExperimentalWarning scripts/check-time-and-toggles.mjs && node --disable-warning=ExperimentalWarning scripts/check-media-and-links.mjs && node --disable-warning=ExperimentalWarning scripts/check-structure.mjs && node --experimental-strip-types --disable-warning=ExperimentalWarning scripts/check-feedback.mjs && node --disable-warning=ExperimentalWarning scripts/check-controls.mjs && node scripts/check-small-pieces.mjs && node --experimental-strip-types --disable-warning=ExperimentalWarning scripts/check-categories.mjs && node --experimental-strip-types --disable-warning=ExperimentalWarning scripts/check-mega-menu.mjs && node --experimental-strip-types --disable-warning=ExperimentalWarning scripts/check-styles.mjs"
+    "check": "node --experimental-strip-types --disable-warning=ExperimentalWarning scripts/check-catalog.mjs && node --disable-warning=ExperimentalWarning scripts/check-business-hours.mjs && node scripts/check-news-ticker.mjs && node --disable-warning=ExperimentalWarning scripts/check-flip-box.mjs && node scripts/check-social-grid.mjs && node --experimental-strip-types --disable-warning=ExperimentalWarning scripts/check-four.mjs && node --disable-warning=ExperimentalWarning scripts/check-video-player.mjs && node scripts/check-cookie-consent.mjs && node --experimental-strip-types --disable-warning=ExperimentalWarning scripts/check-icon.mjs && node --experimental-strip-types --disable-warning=ExperimentalWarning scripts/check-animated-background.mjs && node --disable-warning=ExperimentalWarning scripts/check-modal-and-bar.mjs && node --disable-warning=ExperimentalWarning scripts/check-reveal-cards.mjs && node --disable-warning=ExperimentalWarning scripts/check-time-and-toggles.mjs && node --disable-warning=ExperimentalWarning scripts/check-media-and-links.mjs && node --disable-warning=ExperimentalWarning scripts/check-structure.mjs && node --experimental-strip-types --disable-warning=ExperimentalWarning scripts/check-feedback.mjs && node --disable-warning=ExperimentalWarning scripts/check-controls.mjs && node scripts/check-small-pieces.mjs && node --experimental-strip-types --disable-warning=ExperimentalWarning scripts/check-categories.mjs && node --experimental-strip-types --disable-warning=ExperimentalWarning scripts/check-mega-menu.mjs && node --experimental-strip-types --disable-warning=ExperimentalWarning scripts/check-styles.mjs && node --experimental-strip-types --disable-warning=ExperimentalWarning scripts/check-type.mjs"
   },
   "dependencies": {
     "astro": "^7.2.1"
diff --git a/scripts/check-type.mjs b/scripts/check-type.mjs
new file mode 100644
index 0000000..df63e6c
--- /dev/null
+++ b/scripts/check-type.mjs
@@ -0,0 +1,202 @@
+#!/usr/bin/env node
+/**
+ * The house font set and its pairings in src/data/type.ts -- one file in several repos.
+ *
+ * Downstream copies (the portal's src/brand/type.data.ts, the site's vendored
+ * copy) are byte-identical below the file header and pin the SHA-256 of that
+ * body. This check holds the data's own rules and prints the hash those pins
+ * record:
+ *
+ *   - every FontKey in styles.ts resolves through `familyFor` to a family of that class,
+ *     and the file's written-out FontKey and StyleId unions match styles.ts exactly
+ *   - family and pairing ids are unique, slug-shaped and listed in the same order
+ *     as their id arrays; twelve pairings, one of them "System" at zero bytes
+ *   - every web family is a Fontsource package (`@fontsource-variable/*` when
+ *     variable, `@fontsource/*` when not) under OFL-1.1 or Apache-2.0 and nothing else,
+ *     with its licence URL, designer, 1-4 weights, fallback and metrics
+ *   - the fallback's first face is one the metrics were computed against
+ *   - every pairing names real families, and together they weigh at most TYPE_BUDGET_KB
+ *   - the heading weight is one of the heading family's weights; body text is at 400
+ *   - every family is used by a pairing, and every style board is served by one
+ *   - a pairing serves a board only if its families match the board's heading and body
+ *     classes, and its label class when the board names one, so `type.note` stays true
+ *   - the file imports nothing (framework-free) and its header carries the pin rule
+ *
+ * When you change the body, the hash changes: downstream copies must take the
+ * file again and move their pins in the same change, or their checks fail.
+ *
+ *   node --experimental-strip-types scripts/check-type.mjs
+ */
+import { readFileSync } from 'node:fs';
+import { createHash } from 'node:crypto';
+import { dirname, join } from 'node:path';
+import { fileURLToPath, pathToFileURL } from 'node:url';
+
+const root = join(dirname(fileURLToPath(import.meta.url)), '..');
+const FILE = join(root, 'src/data/type.ts');
+const STYLES = join(root, 'src/data/styles.ts');
+
+const PIN_RULE = 'Only this header may differ; below it the file is one file in every repo.';
+const HEADER_END = '\n */\n';
+const LICENCES = ['OFL-1.1', 'Apache-2.0'];
+// The local faces the metrics are computed against (Capsize's system-font metrics).
+const METRIC_FACES = ['Arial', 'Times New Roman', 'Courier New'];
+const SLUG = /^[a-z0-9]+(-[a-z0-9]+)*$/;
+const PERCENT = /^\d+(\.\d+)?%$/;
+
+const failures = [];
+const fail = (msg) => failures.push(msg);
+
+const src = readFileSync(FILE, 'utf8');
+const at = src.indexOf(HEADER_END);
+if (!src.startsWith('/**') || at === -1) fail('type.ts must open with a block-comment header: the pinned hash is taken below it');
+const header = at === -1 ? '' : src.slice(0, at + HEADER_END.length);
+const body = at === -1 ? src : src.slice(at + HEADER_END.length);
+if (!header.replace(/\n \* ?/g, ' ').includes(PIN_RULE)) fail(`the header must say "${PIN_RULE}"`);
+if (/^\s*import\s/m.test(body) || /\brequire\(/.test(body)) fail('type.ts must import nothing: downstream copies it as plain data');
+
+const T = await import(pathToFileURL(FILE).href);
+const S = await import(pathToFileURL(STYLES).href);
+const fontKeys = Object.keys(S.FONT_STACKS);
+const boards = S.STYLE_BOARDS;
+const families = T.TYPE_FAMILIES;
+const pairings = T.TYPE_PAIRINGS;
+
+// The file's written-out unions match styles.ts.
+const unionOf = (name) => {
+  const m = body.match(new RegExp(`type ${name} =([^;]+);`));
+  return m ? [...m[1].matchAll(/"([^"]+)"/g)].map((x) => x[1]) : [];
+};
+for (const [name, want] of [['FontKey', fontKeys], ['StyleId', [...S.STYLE_IDS]]]) {
+  const got = unionOf(name);
+  if (JSON.stringify(got) !== JSON.stringify(want)) fail(`the ${name} union in type.ts must list, in order, ${want.join(', ')}; it lists ${got.join(', ') || 'nothing'}`);
+}
+
+const short = (what, s, max) => {
+  if (typeof s !== 'string' || !s.trim()) fail(`${what} is empty`);
+  else if (s.length > max) fail(`${what} is ${s.length} characters; at most ${max}`);
+};
+const idsOk = (what, list, declared) => {
+  const ids = list.map((x) => x.id);
+  if (new Set(ids).size !== ids.length) fail(`${what} ids repeat: ${ids.join(', ')}`);
+  for (const id of ids) if (!SLUG.test(id)) fail(`${what} id "${id}" is not slug-shaped`);
+  if (JSON.stringify([...declared]) !== JSON.stringify(ids)) fail(`${what}: the id array and the list name different ids or orders`);
+  return ids;
+};
+
+// Families
+const fids = idsOk('family', families, T.TYPE_FAMILY_IDS);
+const byId = new Map(families.map((f) => [f.id, f]));
+for (const f of families) {
+  const w = `family ${f.id}`;
+  short(`${w}: name`, f.name, 40);
+  short(`${w}: designer`, f.designer, 120);
+  short(`${w}: fallback`, f.fallback, 200);
+  if (!fontKeys.includes(f.class)) fail(`${w}: class "${f.class}" is not a FONT_STACKS key`);
+  const weights = f.weights ?? [];
+  if (weights.length < 1 || weights.length > 4) fail(`${w}: ${weights.length} weights; want one to four`);
+  for (const n of weights) if (!Number.isInteger(n) || n < 100 || n > 900 || n % 100) fail(`${w}: weight ${n} is not one of 100..900`);
+  if (JSON.stringify([...weights]) !== JSON.stringify([...weights].sort((a, b) => a - b))) fail(`${w}: weights must be ascending`);
+
+  if (f.source === 'system') {
+    if (f.package !== null || f.licence !== null || f.licenceUrl !== null) fail(`${w}: a system family has no package, licence or licence URL`);
+    if (f.kb !== 0) fail(`${w}: a system family weighs 0 KB, not ${f.kb}`);
+    if (f.metrics) fail(`${w}: a system family has nothing to swap from, so no metrics`);
+    continue;
+  }
+  if (f.source !== 'fontsource') { fail(`${w}: source "${f.source}"; want fontsource or system`); continue; }
+  if (!LICENCES.includes(f.licence)) fail(`${w}: licence "${f.licence}"; only ${LICENCES.join(' or ')}`);
+  const scope = f.variable ? '@fontsource-variable/' : '@fontsource/';
+  if (typeof f.package !== 'string' || !f.package.startsWith(scope) || !SLUG.test(f.package.slice(scope.length))) {
+    fail(`${w}: package "${f.package}"; a ${f.variable ? 'variable' : 'static'} family comes from ${scope}<slug>`);
+  }
+  let url = null;
+  try { url = new URL(f.licenceUrl); } catch {}
+  if (!url || url.protocol !== 'https:' || !f.licenceUrl.includes(f.package)) fail(`${w}: licenceUrl "${f.licenceUrl}" must be an https URL of the package's own licence`);
+  if (f.variable && !(f.axes ?? []).includes('wght')) fail(`${w}: a variable family lists its axes, wght among them`);
+  if (!f.variable && f.axes !== undefined) fail(`${w}: a static family has no axes`);
+  if (typeof f.kb !== 'number' || !(f.kb > 0) || Math.round(f.kb * 10) !== f.kb * 10) fail(`${w}: kb "${f.kb}" must be a positive number to one decimal`);
+  const first = f.fallback.split(',')[0].trim().replace(/^'|'$/g, '');
+  if (!METRIC_FACES.includes(first)) fail(`${w}: the fallback must start with a face the metrics are computed against (${METRIC_FACES.join(', ')}); it starts with ${first}`);
+  if (!f.metrics) fail(`${w}: no metrics for the fallback @font-face`);
+  for (const [k, v] of Object.entries(f.metrics ?? {})) if (!PERCENT.test(v)) fail(`${w}: metrics.${k} "${v}" is not a percentage`);
+}
+
+// Every board class resolves.
+for (const k of fontKeys) {
+  const f = T.familyFor(k);
+  if (!f) fail(`FontKey "${k}" resolves to no family`);
+  else if (f.class !== k) fail(`familyFor("${k}") gives ${f.id}, of class ${f.class}`);
+}
+
+// Pairings
+if (pairings.length !== 12) fail(`twelve pairings, not ${pairings.length}`);
+idsOk('pairing', pairings, T.TYPE_PAIRING_IDS);
+const used = new Set();
+const served = new Map(boards.map((b) => [b.id, []]));
+const report = [];
+for (const p of pairings) {
+  const w = `pairing ${p.id}`;
+  short(`${w}: name`, p.name, 40);
+  short(`${w}: feel`, p.feel, 120);
+  const fam = {};
+  for (const role of ['heading', 'body', 'label']) {
+    if (p[role] === undefined && role === 'label') continue;
+    const f = byId.get(p[role]);
+    if (!f) { fail(`${w}: ${role} "${p[role]}" is not a family`); continue; }
+    fam[role] = f;
+    used.add(f.id);
+  }
+  const h = p.headings ?? {};
+  if (!(h.scale >= 0.5 && h.scale <= 2)) fail(`${w}: headings.scale ${h.scale}; want 0.5 to 2`);
+  if (fam.heading && !fam.heading.weights.includes(h.weight)) fail(`${w}: headings.weight ${h.weight} is not one of ${fam.heading.id}'s weights (${fam.heading.weights.join(', ')})`);
+  if (!/^(0|-?\d*\.?\d+em)$/.test(h.tracking ?? '')) fail(`${w}: headings.tracking "${h.tracking}"; want 0 or a length in em`);
+  if (typeof h.upper !== 'boolean') fail(`${w}: headings.upper must be true or false`);
+  if (!(h.lineHeight >= 0.8 && h.lineHeight <= 1.6)) fail(`${w}: headings.lineHeight ${h.lineHeight}; want 0.8 to 1.6`);
+  const b = p.bodySettings ?? {};
+  if (!/^\d*\.?\d+rem$/.test(b.size ?? '')) fail(`${w}: bodySettings.size "${b.size}"; want rem`);
+  if (!(b.lineHeight >= 1.3 && b.lineHeight <= 1.9)) fail(`${w}: bodySettings.lineHeight ${b.lineHeight}; want 1.3 to 1.9`);
+  const measure = /^(\d+)ch$/.exec(b.measure ?? '');
+  if (!measure || +measure[1] < 45 || +measure[1] > 80) fail(`${w}: bodySettings.measure "${b.measure}"; want 45ch to 80ch`);
+  if (fam.body && !fam.body.weights.includes(400)) fail(`${w}: body text is set at 400, which ${fam.body.id} does not list`);
+  if (!Array.isArray(p.suits) || p.suits.length < 1 || p.suits.length > 4) fail(`${w}: suits names one to four businesses`);
+  for (const s of p.suits ?? []) short(`${w}: suits entry`, s, 60);
+
+  const kb = T.pairingKb(p);
+  if (kb > T.TYPE_BUDGET_KB) fail(`${w}: its families weigh ${kb} KB; the budget is ${T.TYPE_BUDGET_KB}`);
+
+  if (!p.pairsWith?.length) fail(`${w}: pairsWith names no board`);
+  for (const id of p.pairsWith ?? []) {
+    const board = boards.find((x) => x.id === id);
+    if (!board) { fail(`${w}: pairsWith "${id}" is not a board`); continue; }
+    served.get(id).push(p.id);
+    const t = board.type;
+    for (const role of ['heading', 'body', 'label']) {
+      if (role === 'label' && t.label === undefined) continue;
+      const got = fam[role]?.class;
+      if (got !== t[role]) fail(`${w}: serves ${id}, whose ${role} is ${t[role]} ("${t.note}"), but its ${role} is ${got ?? 'missing'}`);
+    }
+  }
+  report.push(`${p.id} ${kb}KB`);
+}
+for (const id of fids) if (!used.has(id)) fail(`family ${id} is in no pairing: drop it or pair it`);
+for (const [id, ps] of served) if (!ps.length) fail(`board ${id} is served by no pairing`);
+const system = pairings.find((p) => p.id === 'system');
+if (!system || T.pairingKb(system) !== 0) fail('the "system" pairing must be on the list, at zero bytes');
+
+// Constants and helpers
+for (const [k, v] of [['TYPE_PICKS_MAX', 2], ['TYPE_BUDGET_KB', 120]]) {
+  if (T[k] !== v) fail(`${k} is ${T[k]}; want ${v}`);
+}
+if (T.pairingById('nope') !== null || T.pairingById(pairings[0]?.id) !== pairings[0]) fail('pairingById must find a pairing by id and give null for anything else');
+if (T.isPairingId('nope') || !T.isPairingId(pairings[0]?.id)) fail('isPairingId must accept exactly the pairing ids');
+
+if (failures.length) {
+  console.error('check-type failed:');
+  for (const f of failures) console.error(`  - ${f}`);
+  process.exit(1);
+}
+const sha = createHash('sha256').update(body).digest('hex');
+const licences = LICENCES.map((l) => `${families.filter((f) => f.licence === l).length} ${l}`).join(', ');
+console.log(`check-type: ${families.length} families (${licences}, 1 system), ${pairings.length} pairings: ${report.join(', ')}`);
+console.log(`check-type: body SHA-256 ${sha}  (downstream pins record this)`);
diff --git a/src/data/type.ts b/src/data/type.ts
new file mode 100644
index 0000000..1aad3a2
--- /dev/null
+++ b/src/data/type.ts
@@ -0,0 +1,639 @@
+/**
+ * Type: the house font set and its pairings -- SuperheroLibrary, src/data/type.ts. THE SOURCE.
+ *
+ * Copies live downstream, each with its own header and this file's body:
+ *
+ *   ecropolis/SuperheroPortal  src/brand/type.data.ts  (the brand guide's typography, hearts)
+ *
+ * superherotech.ai vendors it too, for the public /type/ page and for /styles/,
+ * which renders each board's type in its real family through `familyFor`.
+ *
+ * Only this header may differ; below it the file is one file in every repo.
+ *
+ * Each downstream repo pins the SHA-256 of everything after this comment, the
+ * way it pins src/data/styles.ts. `npm run check` here prints the hash
+ * (scripts/check-type.mjs). Change the body here first, then take it again
+ * downstream in changes that move their pins to the new hash. A pin is moved
+ * only together with its copy -- otherwise it records the drift instead of
+ * guarding against it.
+ *
+ * This file is data only. No font file is committed to this repo: a site
+ * installs the family's Fontsource `package`, imports its Latin subset and
+ * serves it from its own origin.
+ */
+
+// Framework-free on purpose: no imports, no DOM, no Astro. The portal is a
+// Worker, the site is Astro, and both read this as plain data.
+// Rendering stays in each app; this file only says what the type IS.
+
+/**
+ * The board classes from src/data/styles.ts (`keyof typeof FONT_STACKS`),
+ * written out rather than imported so this file stays importless.
+ * scripts/check-type.mjs holds the two lists equal.
+ */
+type FontKey =
+  | "system"
+  | "geometric"
+  | "mono"
+  | "serif"
+  | "didone"
+  | "humanist"
+  | "rounded"
+  | "hand"
+  | "slab"
+  | "heavy"
+  | "script";
+
+/** The style board ids from src/data/styles.ts, written out for the same reason. */
+type StyleId =
+  | "high-tech"
+  | "minimal"
+  | "classic"
+  | "natural"
+  | "luxurious"
+  | "playful"
+  | "childlike"
+  | "retro"
+  | "bold"
+  | "handcrafted";
+
+/** The family ids, grouped by class in FONT_STACKS order. A class's first family is its default. */
+export const TYPE_FAMILY_IDS = [
+  "system-ui",
+  "inter",
+  "source-sans-3",
+  "nunito-sans",
+  "jost",
+  "jetbrains-mono",
+  "source-serif-4",
+  "lora",
+  "playfair-display",
+  "fraunces",
+  "eb-garamond",
+  "nunito",
+  "comic-neue",
+  "roboto-slab",
+  "archivo",
+  "dancing-script",
+] as const;
+
+export type FamilyId = (typeof TYPE_FAMILY_IDS)[number];
+
+/** The twelve pairing ids, in the order every page shows them. Hearts store these. */
+export const TYPE_PAIRING_IDS = [
+  "system",
+  "quiet",
+  "precise",
+  "counsel",
+  "atelier",
+  "harvest",
+  "old-style",
+  "friendly",
+  "crayon",
+  "diner",
+  "loud",
+  "workshop",
+] as const;
+
+export type PairingId = (typeof TYPE_PAIRING_IDS)[number];
+
+/** A client hearts up to two pairings. */
+export const TYPE_PICKS_MAX = 2;
+
+/** The most a pairing's families may weigh together, in KB of Latin woff2. */
+export const TYPE_BUDGET_KB = 120;
+
+/** The only two licences a family may carry. Both allow the files to be redistributed and self-hosted. */
+export type TypeLicence = "OFL-1.1" | "Apache-2.0";
+
+/**
+ * A family. Every web family is a Fontsource package under OFL-1.1 or
+ * Apache-2.0, checked against the package's own LICENSE at the version below.
+ *
+ * One family is not a download: `system-ui`, the device's own sans. It has
+ * `source: "system"`, no package, no licence and zero bytes, so the "System"
+ * pairing costs nothing and stays a legitimate choice.
+ *
+ * - `kb` is the Latin-subset upright woff2 a site loads, measured from
+ *   Fontsource 5.3.0 (every package here is at 5.3.0), in KB of 1024 bytes to
+ *   one decimal. For a variable family that is the `wght` file its default
+ *   import (`index.css`) serves, which covers every weight; for a static one
+ *   it is the sum of the listed `weights`. Italics are extra and load only
+ *   where a page uses them.
+ * - `axes` lists the axes the font has; the `wght` file carries only `wght`.
+ *   The other axes (opsz, SOFT, wdth, ...) need the package's larger files.
+ * - `weights` is what the pairings use, at most four.
+ * - `fallback` is a local stack. `metrics` is for a fallback `@font-face`
+ *   whose `src` is `local()` of the FIRST face in `fallback`, so the swap to
+ *   the web font does not move the layout. The numbers are Capsize's
+ *   (`@capsizecss/core` 4.1.3 `createFontStack`) with the web font measured
+ *   from the Fontsource woff2 itself by `@capsizecss/unpack` 4.0.1 and the
+ *   fallback's from `@capsizecss/metrics` 4.3.0; rounded to two decimals.
+ */
+export interface TypeFamily {
+  id: FamilyId;
+  /** The family's own name: "Inter". The CSS name is `cssFamily(f)`. */
+  name: string;
+  /** The board class it stands in for. Every FontKey has at least one family. */
+  class: FontKey;
+  source: "fontsource" | "system";
+  /** "@fontsource-variable/inter"; null only for the system family. */
+  package: string | null;
+  licence: TypeLicence | null;
+  /** The LICENSE file shipped in the package, at the version measured. */
+  licenceUrl: string | null;
+  designer: string;
+  variable: boolean;
+  axes?: readonly string[];
+  weights: readonly number[];
+  fallback: string;
+  metrics?: { sizeAdjust: string; ascentOverride?: string; descentOverride?: string; lineGapOverride?: string };
+  kb: number;
+}
+
+export interface TypePairing {
+  id: PairingId;
+  name: string;
+  heading: FamilyId;
+  body: FamilyId;
+  /** A third face for small labels, eyebrows or figures, when the pairing has one. */
+  label?: FamilyId;
+  /** One line, at most 120 characters: what the pairing feels like. */
+  feel: string;
+  /**
+   * The recommended heading settings. `scale` multiplies the site's heading
+   * sizes; `tracking` is CSS letter-spacing; `lineHeight` is unitless.
+   */
+  headings: { scale: number; weight: number; tracking: string; upper: boolean; lineHeight: number };
+  /** Body text: CSS font-size, unitless line-height, and max-width in ch. */
+  bodySettings: { size: string; lineHeight: number; measure: string };
+  /** The kinds of business it suits. */
+  suits: readonly string[];
+  /**
+   * The style boards it serves. A board listed here has its heading and body
+   * classes matched by this pairing's families, and its label class too when
+   * the board names one, so the board's `type.note` stays true of it.
+   */
+  pairsWith: readonly StyleId[];
+}
+
+const SANS = "Arial, Helvetica, sans-serif";
+const SERIF = "'Times New Roman', Times, serif";
+const MONO = "'Courier New', Courier, monospace";
+const LICENCE = (pkg: string) => `https://cdn.jsdelivr.net/npm/${pkg}@5.3.0/LICENSE`;
+
+export const TYPE_FAMILIES: readonly TypeFamily[] = [
+  /* ------------------------------------------------------------- system */
+  {
+    id: "system-ui",
+    name: "System UI",
+    class: "system",
+    source: "system",
+    package: null,
+    licence: null,
+    licenceUrl: null,
+    designer: "The device's own: San Francisco, Segoe UI, Roboto",
+    variable: false,
+    weights: [400, 500, 600, 700],
+    fallback: "ui-sans-serif, system-ui, -apple-system, 'Segoe UI', Roboto, Helvetica, Arial, sans-serif",
+    kb: 0,
+  },
+  {
+    id: "inter",
+    name: "Inter",
+    class: "system",
+    source: "fontsource",
+    package: "@fontsource-variable/inter",
+    licence: "OFL-1.1",
+    licenceUrl: LICENCE("@fontsource-variable/inter"),
+    designer: "Rasmus Andersson",
+    variable: true,
+    axes: ["wght", "opsz"],
+    weights: [400, 500, 700],
+    fallback: SANS,
+    metrics: { sizeAdjust: "107.12%", ascentOverride: "90.44%", descentOverride: "22.52%", lineGapOverride: "0%" },
+    kb: 47.1,
+  },
+  {
+    id: "source-sans-3",
+    name: "Source Sans 3",
+    class: "system",
+    source: "fontsource",
+    package: "@fontsource-variable/source-sans-3",
+    licence: "OFL-1.1",
+    licenceUrl: LICENCE("@fontsource-variable/source-sans-3"),
+    designer: "Paul D. Hunt for Adobe",
+    variable: true,
+    axes: ["wght"],
+    weights: [400, 600],
+    fallback: SANS,
+    metrics: { sizeAdjust: "89.28%", ascentOverride: "114.7%", descentOverride: "44.8%", lineGapOverride: "0%" },
+    kb: 28.1,
+  },
+  {
+    id: "nunito-sans",
+    name: "Nunito Sans",
+    class: "system",
+    source: "fontsource",
+    package: "@fontsource-variable/nunito-sans",
+    licence: "OFL-1.1",
+    licenceUrl: LICENCE("@fontsource-variable/nunito-sans"),
+    designer: "Vernon Adams, Jacques Le Bailly, Manvel Shmavonyan, Alexei Vanyashin",
+    variable: true,
+    axes: ["wght", "wdth", "opsz", "YTLC"],
+    weights: [400, 700],
+    fallback: SANS,
+    metrics: { sizeAdjust: "97.8%", ascentOverride: "103.37%", descentOverride: "36.09%", lineGapOverride: "0%" },
+    kb: 30.3,
+  },
+  /* ---------------------------------------------------------- geometric */
+  {
+    id: "jost",
+    name: "Jost",
+    class: "geometric",
+    source: "fontsource",
+    package: "@fontsource-variable/jost",
+    licence: "OFL-1.1",
+    licenceUrl: LICENCE("@fontsource-variable/jost"),
+    designer: "Owen Earl (indestructible type*)",
+    variable: true,
+    axes: ["wght"],
+    weights: [400, 500, 600],
+    fallback: SANS,
+    metrics: { sizeAdjust: "96.01%", ascentOverride: "111.45%", descentOverride: "39.06%", lineGapOverride: "0%" },
+    kb: 26,
+  },
+  /* --------------------------------------------------------------- mono */
+  {
+    id: "jetbrains-mono",
+    name: "JetBrains Mono",
+    class: "mono",
+    source: "fontsource",
+    package: "@fontsource-variable/jetbrains-mono",
+    licence: "OFL-1.1",
+    licenceUrl: LICENCE("@fontsource-variable/jetbrains-mono"),
+    designer: "Philipp Nurullin and Konstantin Bulenkov for JetBrains",
+    variable: true,
+    axes: ["wght"],
+    weights: [400, 500],
+    fallback: MONO,
+    metrics: { sizeAdjust: "99.98%", ascentOverride: "102.02%", descentOverride: "30%", lineGapOverride: "0%" },
+    kb: 39.5,
+  },
+  /* -------------------------------------------------------------- serif */
+  {
+    id: "source-serif-4",
+    name: "Source Serif 4",
+    class: "serif",
+    source: "fontsource",
+    package: "@fontsource-variable/source-serif-4",
+    licence: "OFL-1.1",
+    licenceUrl: LICENCE("@fontsource-variable/source-serif-4"),
+    designer: "Frank Grießhammer for Adobe",
+    variable: true,
+    axes: ["wght", "opsz"],
+    weights: [400, 600, 700],
+    fallback: SERIF,
+    metrics: { sizeAdjust: "117.91%", ascentOverride: "87.87%", descentOverride: "28.41%", lineGapOverride: "0%" },
+    kb: 49.6,
+  },
+  {
+    id: "lora",
+    name: "Lora",
+    class: "serif",
+    source: "fontsource",
+    package: "@fontsource-variable/lora",
+    licence: "OFL-1.1",
+    licenceUrl: LICENCE("@fontsource-variable/lora"),
+    designer: "Olga Karpushina for Cyreal",
+    variable: true,
+    axes: ["wght"],
+    weights: [400, 500, 600],
+    fallback: SERIF,
+    metrics: { sizeAdjust: "115.2%", ascentOverride: "87.33%", descentOverride: "23.78%", lineGapOverride: "0%" },
+    kb: 36.9,
+  },
+  /* ------------------------------------------------------------- didone */
+  {
+    id: "playfair-display",
+    name: "Playfair Display",
+    class: "didone",
+    source: "fontsource",
+    package: "@fontsource-variable/playfair-display",
+    licence: "OFL-1.1",
+    licenceUrl: LICENCE("@fontsource-variable/playfair-display"),
+    designer: "Claus Eggers Sørensen",
+    variable: true,
+    axes: ["wght"],
+    weights: [400, 600],
+    fallback: SERIF,
+    metrics: { sizeAdjust: "111.26%", ascentOverride: "97.25%", descentOverride: "22.56%", lineGapOverride: "0%" },
+    kb: 37.5,
+  },
+  /* ----------------------------------------------------------- humanist */
+  {
+    id: "fraunces",
+    name: "Fraunces",
+    class: "humanist",
+    source: "fontsource",
+    package: "@fontsource-variable/fraunces",
+    licence: "OFL-1.1",
+    licenceUrl: LICENCE("@fontsource-variable/fraunces"),
+    designer: "Undercase Type (Phaedra Charles, Flavia Zimbardi)",
+    variable: true,
+    axes: ["wght", "opsz", "SOFT", "WONK"],
+    weights: [400, 600],
+    fallback: SERIF,
+    metrics: { sizeAdjust: "127.02%", ascentOverride: "77%", descentOverride: "20.08%", lineGapOverride: "0%" },
+    kb: 35.8,
+  },
+  {
+    id: "eb-garamond",
+    name: "EB Garamond",
+    class: "humanist",
+    source: "fontsource",
+    package: "@fontsource-variable/eb-garamond",
+    licence: "OFL-1.1",
+    licenceUrl: LICENCE("@fontsource-variable/eb-garamond"),
+    designer: "Georg Duffner and Octavio Pardo",
+    variable: true,
+    axes: ["wght"],
+    weights: [400, 500, 600],
+    fallback: SERIF,
+    metrics: { sizeAdjust: "94.77%", ascentOverride: "106.26%", descentOverride: "31.44%", lineGapOverride: "0%" },
+    kb: 43.3,
+  },
+  /* ------------------------------------------------------------ rounded */
+  {
+    id: "nunito",
+    name: "Nunito",
+    class: "rounded",
+    source: "fontsource",
+    package: "@fontsource-variable/nunito",
+    licence: "OFL-1.1",
+    licenceUrl: LICENCE("@fontsource-variable/nunito"),
+    designer: "Vernon Adams, Cyreal and Jacques Le Bailly",
+    variable: true,
+    axes: ["wght"],
+    weights: [400, 700, 800],
+    fallback: SANS,
+    metrics: { sizeAdjust: "97.8%", ascentOverride: "103.37%", descentOverride: "36.09%", lineGapOverride: "0%" },
+    kb: 38.2,
+  },
+  /* --------------------------------------------------------------- hand */
+  {
+    id: "comic-neue",
+    name: "Comic Neue",
+    class: "hand",
+    source: "fontsource",
+    package: "@fontsource/comic-neue",
+    licence: "OFL-1.1",
+    licenceUrl: LICENCE("@fontsource/comic-neue"),
+    designer: "Craig Rozynski",
+    variable: false,
+    weights: [700],
+    fallback: SANS,
+    metrics: { sizeAdjust: "98.47%", ascentOverride: "91.39%", descentOverride: "25.39%", lineGapOverride: "0%" },
+    kb: 18.8,
+  },
+  /* --------------------------------------------------------------- slab */
+  {
+    id: "roboto-slab",
+    name: "Roboto Slab",
+    class: "slab",
+    source: "fontsource",
+    package: "@fontsource-variable/roboto-slab",
+    licence: "Apache-2.0",
+    licenceUrl: LICENCE("@fontsource-variable/roboto-slab"),
+    designer: "Christian Robertson",
+    variable: true,
+    axes: ["wght"],
+    weights: [400, 700],
+    fallback: SERIF,
+    metrics: { sizeAdjust: "116.83%", ascentOverride: "89.69%", descentOverride: "23.2%", lineGapOverride: "0%" },
+    kb: 33.4,
+  },
+  /* -------------------------------------------------------------- heavy */
+  {
+    id: "archivo",
+    name: "Archivo",
+    class: "heavy",
+    source: "fontsource",
+    package: "@fontsource-variable/archivo",
+    licence: "OFL-1.1",
+    licenceUrl: LICENCE("@fontsource-variable/archivo"),
+    designer: "Héctor Gatti for Omnibus-Type",
+    variable: true,
+    axes: ["wght", "wdth"],
+    weights: [700, 900],
+    fallback: SANS,
+    metrics: { sizeAdjust: "102.29%", ascentOverride: "85.84%", descentOverride: "20.53%", lineGapOverride: "0%" },
+    kb: 34.1,
+  },
+  /* ------------------------------------------------------------- script */
+  {
+    id: "dancing-script",
+    name: "Dancing Script",
+    class: "script",
+    source: "fontsource",
+    package: "@fontsource-variable/dancing-script",
+    licence: "OFL-1.1",
+    licenceUrl: LICENCE("@fontsource-variable/dancing-script"),
+    designer: "Pablo Impallari",
+    variable: true,
+    axes: ["wght"],
+    weights: [500],
+    fallback: SERIF,
+    metrics: { sizeAdjust: "89.35%", ascentOverride: "102.96%", descentOverride: "31.34%", lineGapOverride: "0%" },
+    kb: 41.7,
+  },
+];
+
+export const TYPE_PAIRINGS: readonly TypePairing[] = [
+  {
+    id: "system",
+    name: "System",
+    heading: "system-ui",
+    body: "system-ui",
+    feel: "Nothing to download: the device's own sans, quick and familiar on every screen.",
+    headings: { scale: 1, weight: 500, tracking: "-0.01em", upper: false, lineHeight: 1.15 },
+    bodySettings: { size: "1rem", lineHeight: 1.55, measure: "68ch" },
+    suits: ["Any site where speed matters most", "Portals and internal tools"],
+    pairsWith: ["minimal"],
+  },
+  {
+    id: "quiet",
+    name: "Quiet",
+    heading: "inter",
+    body: "inter",
+    feel: "One neutral sans at light weights; the work and the white space do the talking.",
+    headings: { scale: 0.95, weight: 500, tracking: "-0.02em", upper: false, lineHeight: 1.15 },
+    bodySettings: { size: "1rem", lineHeight: 1.6, measure: "66ch" },
+    suits: ["Architects and designers", "Studios and consultancies"],
+    pairsWith: ["minimal"],
+  },
+  {
+    id: "precise",
+    name: "Precise",
+    heading: "jost",
+    body: "inter",
+    label: "jetbrains-mono",
+    feel: "Geometric headings over a neutral text face, with a monospace detail for figures and labels.",
+    headings: { scale: 1, weight: 600, tracking: "-0.02em", upper: false, lineHeight: 1.1 },
+    bodySettings: { size: "1rem", lineHeight: 1.6, measure: "68ch" },
+    suits: ["Software and tech services", "Engineering firms"],
+    pairsWith: ["high-tech"],
+  },
+  {
+    id: "counsel",
+    name: "Counsel",
+    heading: "source-serif-4",
+    body: "source-sans-3",
+    feel: "A serif and a sans drawn as one family: steady, legible and unfussy.",
+    headings: { scale: 1, weight: 600, tracking: "0", upper: false, lineHeight: 1.2 },
+    bodySettings: { size: "1.0625rem", lineHeight: 1.6, measure: "66ch" },
+    suits: ["Accountants, lawyers and advisers", "Charities and member bodies"],
+    pairsWith: ["classic"],
+  },
+  {
+    id: "atelier",
+    name: "Atelier",
+    heading: "playfair-display",
+    body: "source-serif-4",
+    feel: "A high-contrast display serif, spaced out in capitals, over a calm text serif.",
+    headings: { scale: 0.85, weight: 400, tracking: "0.08em", upper: true, lineHeight: 1.2 },
+    bodySettings: { size: "1.0625rem", lineHeight: 1.65, measure: "64ch" },
+    suits: ["Jewellers and fine goods", "Boutique hotels and restaurants"],
+    pairsWith: ["luxurious"],
+  },
+  {
+    id: "harvest",
+    name: "Harvest",
+    heading: "fraunces",
+    body: "nunito-sans",
+    feel: "A soft, warm serif with a gentle sans: grown rather than built.",
+    headings: { scale: 1, weight: 600, tracking: "-0.01em", upper: false, lineHeight: 1.15 },
+    bodySettings: { size: "1.0625rem", lineHeight: 1.6, measure: "66ch" },
+    suits: ["Farms and food producers", "Cafés and bakeries"],
+    pairsWith: ["natural"],
+  },
+  {
+    id: "old-style",
+    name: "Old style",
+    heading: "eb-garamond",
+    body: "nunito-sans",
+    feel: "A Renaissance book face over a soft sans: warm, literate and unhurried.",
+    headings: { scale: 1.1, weight: 500, tracking: "0", upper: false, lineHeight: 1.15 },
+    bodySettings: { size: "1.0625rem", lineHeight: 1.6, measure: "66ch" },
+    suits: ["Wineries and heritage estates", "Bookshops and publishers"],
+    pairsWith: ["natural"],
+  },
+  {
+    id: "friendly",
+    name: "Friendly",
+    heading: "nunito",
+    body: "nunito",
+    feel: "One round-ended sans, heavy for headings and light for text: cheerful and easy to read.",
+    headings: { scale: 1.05, weight: 800, tracking: "-0.01em", upper: false, lineHeight: 1.1 },
+    bodySettings: { size: "1.0625rem", lineHeight: 1.6, measure: "64ch" },
+    suits: ["Local shops and repairs", "Pet care and family services"],
+    pairsWith: ["playful"],
+  },
+  {
+    id: "crayon",
+    name: "Crayon",
+    heading: "comic-neue",
+    body: "nunito",
+    feel: "Big hand-lettered headings over a round sans that children and parents both find easy.",
+    headings: { scale: 1.1, weight: 700, tracking: "0", upper: false, lineHeight: 1.1 },
+    bodySettings: { size: "1.125rem", lineHeight: 1.6, measure: "60ch" },
+    suits: ["Nurseries and children's services", "Schools and clubs"],
+    pairsWith: ["childlike"],
+  },
+  {
+    id: "diner",
+    name: "Diner",
+    heading: "roboto-slab",
+    body: "inter",
+    feel: "A sturdy slab for signs and headings, a plain sans for the menu.",
+    headings: { scale: 1, weight: 700, tracking: "0.02em", upper: true, lineHeight: 1.1 },
+    bodySettings: { size: "1rem", lineHeight: 1.6, measure: "66ch" },
+    suits: ["Diners, cafés and bars", "Hardware stores and trades"],
+    pairsWith: ["retro"],
+  },
+  {
+    id: "loud",
+    name: "Loud",
+    heading: "archivo",
+    body: "inter",
+    feel: "Huge, heavy, tight capitals over a plain sans that stays out of the way.",
+    headings: { scale: 1.35, weight: 900, tracking: "-0.03em", upper: true, lineHeight: 0.95 },
+    bodySettings: { size: "1rem", lineHeight: 1.55, measure: "64ch" },
+    suits: ["Gyms and fitness", "Events and promoters"],
+    pairsWith: ["bold"],
+  },
+  {
+    id: "workshop",
+    name: "Workshop",
+    heading: "lora",
+    body: "source-sans-3",
+    label: "dancing-script",
+    feel: "A brushed, calligraphic serif and a clear sans, with a script for the maker's signature.",
+    headings: { scale: 1, weight: 600, tracking: "0", upper: false, lineHeight: 1.2 },
+    bodySettings: { size: "1.0625rem", lineHeight: 1.6, measure: "66ch" },
+    suits: ["Makers and craft studios", "Florists and gift shops"],
+    pairsWith: ["handcrafted"],
+  },
+];
+
+/* ------------------------------------------------------------------- helpers */
+
+export function isFamilyId(v: unknown): v is FamilyId {
+  return typeof v === "string" && (TYPE_FAMILY_IDS as readonly string[]).includes(v);
+}
+
+export function isPairingId(v: unknown): v is PairingId {
+  return typeof v === "string" && (TYPE_PAIRING_IDS as readonly string[]).includes(v);
+}
+
+/** A family by id, or null for anything that is not one. */
+export function familyById(id: string | null | undefined): TypeFamily | null {
+  if (typeof id !== "string") return null;
+  return TYPE_FAMILIES.find((f) => f.id === id) ?? null;
+}
+
+/** A pairing by id, or null for anything that is not one of the twelve. Never the nearest pairing. */
+export function pairingById(id: string | null | undefined): TypePairing | null {
+  if (typeof id !== "string") return null;
+  return TYPE_PAIRINGS.find((p) => p.id === id) ?? null;
+}
+
+/**
+ * The family a board class renders in: the first family of that class, in
+ * TYPE_FAMILIES order. Every FontKey has one (scripts/check-type.mjs holds it),
+ * and `system` resolves to the device's own sans, as the boards always drew it.
+ */
+export function familyFor(key: FontKey): TypeFamily {
+  return TYPE_FAMILIES.find((f) => f.class === key)!;
+}
+
+/**
+ * The CSS name Fontsource registers the family under: "Inter Variable" for a
+ * variable package, "Comic Neue" for a static one. Null for the system family,
+ * which is its `fallback` stack alone.
+ */
+export function cssFamily(f: TypeFamily): string | null {
+  if (f.source === "system") return null;
+  return f.variable ? `${f.name} Variable` : f.name;
+}
+
+/** The families a pairing loads -- heading, body and label, each once. */
+export function pairingFamilies(p: TypePairing): TypeFamily[] {
+  const ids = [p.heading, p.body, ...(p.label ? [p.label] : [])];
+  return [...new Set(ids)].map((id) => familyById(id)!);
+}
+
+/** What a pairing costs to load, in KB of Latin woff2, to one decimal. */
+export function pairingKb(p: TypePairing): number {
+  return Math.round(pairingFamilies(p).reduce((sum, f) => sum + f.kb, 0) * 10) / 10;
+}