Case Study Lessons — Duolingo Design

Coverage status (2026-07-13)

Playwright full-text scrape: 17/17 pages OK (hub + 16 content routes). Raw extracts live in research/case-studies/raw/duolingo-*.md + inventory.json.

Public site is a brand bible SPA (not a product component system). Canonical content inventory:

Identity

/identity/logos — clear space, min size, lockups, misuse
/identity/color — named digital/print values
/identity/typography — custom + fallback stacks
/identity/imagery — photo/image direction
/identity/brand-family — sub-brand construction

Writing

/writing/brand-narrative
/writing/voice
/writing/tone
/writing/duo — character verbal contract
/writing/style
/writing/glossary — canonical/prohibited terms

Illustration

/illustration/shape-language
/illustration/duo — construction
/illustration/characters

Other

/marketing/assets
/resources

What was already known vs fully operationalized in AwesomeDS

Lesson	Prior ADS	Now
Brand personality as system	thin brand modules	cross-medium contract
Voice/tone matrices	partial content-design	full matrix template
Character production grammar	illustration stub	character-system module
Page pattern principle→example→misuse	uneven	documented sequence
Product UI / a11y / motion on Duolingo site	N/A (not published there)	covered by other sources

Transferable principles (anti-imitation)

Personality is a production system, not adjectives.
Writing systems need glossary + forbidden terms.
Illustration needs geometry + complexity budget + misuse gallery.
Characters need anatomy + emotion limits + who may speak.
Sub-brands inherit with explicit family rules.
Public brand sites can still be product-stale — revalidate facts.

Historical fossils warning

Treat product stats, plan names (e.g. legacy Plus), OS version examples, and learner counts as historical, not current product truth.

Linked rules

rule.brand.cross-medium-coherence
rule.brand.content-design
rule.brand.illustration-grammar

Operational depth

Registration is not absorption. The route-by-route completion audit is research/duolingo-complete-audit-2026-07.md; the resulting executable, brand-neutral production doctrine lives in brand/duolingo-derived/.