# Mobile UI

> Use when a ticket builds or reworks UI in a React Native / Expo (or React + Capacitor) mobile app and it must feel like a real, store-credible native app — not a wrapped mobile website. Covers the native-feel bar, safe-area/gesture/haptics, store-readiness, and mobile performance. Invoke for "make this screen feel native", "build the mobile X screen", "this feels like a website", "would this get approved", or as the mobile pack for any app-UI change.

- Skill: `tmj-90/mobile-ui` (Agent Skill)
- Install (CLI): `npx skillmds@latest add tmj-90/mobile-ui`
- Raw SKILL.md: https://api.skillmd.com/api/skills/tmj-90/mobile-ui/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Web & Frontend
- Author: tmj-90 (https://skillmd.com/u/tmj-90)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/tmj-90/mobile-ui

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# Build store-credible native-feel mobile UI

Change the **skin, never the skeleton.** Build mobile UI that clears a native-feel bar and
a store-readiness bar — without touching gameplay, navigation routes, state, scoring, or
business logic. Where a redesign implies a structural change ("this should be a sheet, not a
modal"), flag it as a **proposal**; do not silently implement it.

## The three non-negotiable bars

A "premium" mobile surface must clear all three at once — failing any one ships as
not-premium regardless of the others.

1. **Native feel.** Every hybrid/RN screen reads as a mobile website until deliberately
   de-websified. Tells to close: centred modals (→ bottom sheets), fade transitions
   (→ slide/shared-element), missing swipe-back and hardware-back handling, no haptics on
   primary taps, fonts flashing, wrong scroll bounce, ignored safe-area insets, default
   launch screen.
2. **Maturity (indie → store-credible).** Tidying a plateau makes the plateau more visible.
   Recommit: real type scale, brand chrome (not generic), activated margins, ambient life,
   and **one named hero detail per screen** — the deliberate moment the user remembers.
3. **Store readiness.** Most "wouldn't get approved" intuition is a finite checklist:
   tap targets ≥ 44pt, privacy/permission strings present, real launch screen, Dynamic
   Type / large-text support, working hardware back (Android), opposite colour scheme,
   no placeholder content.

## Steps

1. **Read the lore + brand/tokens first.** `search_lore` (Memory MCP) and any
   `BRAND.md`/`DESIGN.md`/`tokens` file. If a brand/design system exists, **extend it in
   its idiom** (Brand-Respecting Mode) — audit + close gaps; do not re-pitch the aesthetic.
   Confirm the stack (RN/Expo or React + Capacitor) and match its component conventions.
2. **Audit the screen** against the three bars: score native-feel per item, diagnose
   maturity, pre-screen store-rejection triggers. Note gameplay/logic surfaces to leave alone.
3. **Respect safe areas.** Use the safe-area insets (`react-native-safe-area-context` /
   the env-inset equivalent) for top/bottom/notch; never hardcode status-bar heights.
4. **Gestures + navigation feel native.** Swipe-back, hardware back (Android), bottom
   sheets over centred modals, slide/shared-element transitions over fades. Keep the
   navigation routes and actions exactly as they are.
5. **Haptics + sound hooks** on primary interactions (selection, confirm, error) via the
   platform haptics API — subtle, consistent, behind a tokenised hook.
6. **Tokens drive presentation** — colour, type scale, spacing, motion, radius. No raw hex
   or magic numbers in components; scrolls hide scrollbars, use momentum, and disable global
   pull-to-refresh except where intended.
7. **Performance:** keep the main interaction loop at 60fps; animate on the native driver
   (`useNativeDriver: true` / Reanimated worklets); virtualise long lists (`FlatList`/
   `FlashList`); avoid layout thrash and oversized images.
8. **Verify + evidence.** Run the repo's tests + lint; a migration ends **green** — a
   failing gameplay test means logic changed (roll back, never edit the test to pass). Add
   tests for new visual contracts (component states, screen smoke tests). Record
   `test_output` via `record-evidence` and submit for review.

## Build / Test

- Run the repo's configured test + lint; type-check (`tsc --noEmit`) for TS.
- Every screen migration ends green with a successful build; default failing tests to
  **roll back the migration**, never to modifying the test.
- Prefer screenshot/visual checks on a real device or simulator at the supported tiers;
  test with Reduce Motion, large text (200%), VoiceOver/TalkBack, and the opposite colour scheme.
- The DoD is verified by the repo's configured commands — record the output as evidence.

## Review checklist (a mobile reviewer must check)

- **No web-hybrid tells** — bottom sheets not centred modals, slide not fade, swipe-back +
  hardware-back work, no font flash, scroll bounce/momentum correct.
- **Safe-area insets honoured** — nothing under the notch / home indicator; no hardcoded bar heights.
- **Haptics on primary taps**, consistent and subtle.
- **Tap targets ≥ 44pt**; Dynamic Type / large-text supported; opposite colour scheme holds.
- **One hero detail per screen** named and present; type scale + chrome are committed, not generic.
- **Tokens, not hardcoded** colour/spacing/type; no raw hex / magic numbers in components.
- **Performance** — native-driver animation, virtualised long lists, 60fps on the main loop.
- **Skeleton preserved** — routes, navigation actions, state, scoring, and component
  prop/event contracts unchanged; structural changes raised as proposals, not silently made.
- **Store triggers cleared** — privacy strings, real launch screen, no placeholder content.

## Rules

- Change the skin, never the skeleton — no logic/navigation/state/scoring changes.
- Clear all three bars (native feel, maturity, store readiness) — failing one fails the surface.
- Safe-area insets, native gestures, haptics, native-driver animation — no hardcoded bar heights.
- Tokens for all presentation; structural changes are proposals, not silent edits; tests stay green.

## Capture lore

This skill is one of the places durable, reusable knowledge naturally surfaces:
**A mobile convention this repo enforces — the design system/tokens, brand voice, a native-feel pattern, a store-submission requirement, or a "never touch" gameplay/logic boundary.** That kind of fact is *lore*. Capture it via the **lore-capture
protocol in your brief** (`CLAUDE.factory.md`, step 11 "Memory contribution"):
call the Memory MCP `suggest_lore` once at the close of your work — reusable
conventions, gotchas, decisions, and boundaries only, never per-ticket trivia.