Personality is a contract across UI, words, illustration, and motion. Principles - Define brand personality as verbs (encourages, clarifies, celebrates) not adjectives alone. - Voice/tone matrices cover success, error,

Copyright-safe synthesis of production patterns popularized by brand systems like Duolingo's public illustration bible. When to use a character - Teaching, celebration, empty states, onboarding — not security/legal. -

Rules - Prefer concrete verbs and user-centered outcomes. - Error copy names the problem and the next action. - Maintain a glossary for product nouns; forbid overloaded terms. - Japanese: respect です/ます consistency per su

Duolingo Design's strongest transferable lesson: one declared personality propagates into words, shapes, color, imagery, assets, and hard production constraints — not a palette + logo kit. The contract (required fields

These modules extract transferable production-system lessons from the complete Duolingo Design audit. They do not reproduce Duolingo's identity, assets, voice, geometry, palette, typography, character, or copy. Use the

Principle A brand kit is a versioned product surface. Guidance without usable, licensed, traceable artifacts is incomplete; a download folder without governance is a liability. Asset manifest Every asset declares sta

Principle Sub-brands are governance decisions before they are lockups. Visual novelty is not a reason to fragment recognition. Architecture choices Choose and document one relationship per offering: master-branded, e

Principle Typography is a system of roles and measurable constraints. A recognizable display face never excuses illegibility, missing scripts, or unlicensed use. Required contract For every role record family, source

Principle Character motion is behavior, not mascot decoration. One cross-modal contract must align anatomy, personality, speech authority, emotion, movement, sound, context, accessibility, and performance. Demonstration

Principle Editorial style is executable policy by locale and channel. Universal rules cover clarity and harm; locale profiles own grammar and convention. Profile schema Each profile declares locale, channel, owner, r

Principle Photography, illustration, diagrams, and synthetic images have different jobs. Choose the medium from communication intent, not novelty or convenience. Decision contract Use photography for credible people,

Principle A logo system is a responsive interface, not one file. Define the mark roles before drawing variants. Original artwork is mandatory; never derive geometry from a reference brand. Required contract Each vari

Principle Narrative is an evidence-backed decision system, not inspirational prose. Mission explains why; difference explains the credible choice; proof supports it; audience messages adapt relevance without changing tr

Principle A product lexicon is governed domain data. It connects public language, internal concepts, UI strings, localization, analytics, code, and support. Term record Each canonical term declares stable ID, display

Rules - One geometric grammar per brand (corner radius, stroke, perspective). - Icons must remain legible at 16px and meet contrast on target surfaces. - Character systems need proportion sheets and emotion limits. Lin

Many elite consumer brands treat sonic identity as part of the same personality contract as color and type (Apple HIG audio guidance, game/learning apps, hardware brands). Principles 1. Sound communicates state, not n

Synthesized from Duolingo writing system structure + Carbon/Polaris/Atlassian content patterns (transferable; not a copy of any brand voice). Voice vs tone - Voice = stable personality (always true). - Tone = situatio