Mobile app UI design expert for iOS and Android. Use when designing app interfaces, creating design systems, ensuring accessibility, or following platform guidelines. Covers Material Design 3, Human Interface Guidelines, color theory, typography, and 2025 trends.

Mobile App UI Design Expert guidance for designing beautiful, accessible, and platform native mobile app interfaces following 2025 best practices. Core Philosophy User First Design — Prioritize user needs, behaviors, and mental models over aesthetics Platform Consistency — Follow iOS HIG and Android Material Design guidelines Accessibility as Foundation — Design for all users from the start, not as an afterthought Emotional Intelligence — Create interfaces that users emotionally connect with Performance Conscious — Beautiful design that doesn't sacrifice app performance Hard Rules (Must Follow) These rules are mandatory. Violating them means the skill is not working correctly. Accessibility First All designs must meet WCAG 2.2 AA standards. Accessibility is not optional. Platform Guidelines Adherence Follow platform specific design guidelines. Do not mix iOS and Android patterns. Consistent Design System Every app must have a documented design system with tokens. Touch Friendly Design All interactive elements must be optimized for touch interaction. Quick Reference When to Use What Scenario Approach Key Considerations New app design Start with design system Define tokens before screens iOS only app Human Interface Guidelines SF Pro, standard iOS patterns Android only app Material Design 3 Roboto, Material components Cross platform app Adaptive design Platform specific navigation Redesign existing app Audit first Maintain mental models Accessibility review WCAG 2.2 AA checklist Contrast, touch targets, labels Design System Fundamentals Color System Typography Scale Spacing System Platform Guidelines iOS Human Interface Guidelines Android Material Design 3 2025 Design Trends AI Driven Personalization Dark Mode Excellence Microinteractions Glassmorphism & Neumorphism Extended Reference Detailed material starting at Accessibility Checklist has been moved to [ reference/extended.md ](reference/extended.md) to keep this skill concise. Load that reference when the task requires the moved examples, command catalogs, checklists, platform details, or implementation templates.

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