UI Reasoning: Expense Splitter / Bill Split. Recommended Pattern: Minimal & Direct + Demo. Style Priority: Flat Design + Vibrant & Block-based. Color Mood: Success green + alert red + neutral grey + avatar accent colors. Typography Mood: Bold + Clean + Sans-serif. Key Effects: Color shift hover + Fast 150ms transitions + No shadows. Decision Rules: {"if_ux_focused": "prioritize-clarity", "if_mobile": "optimize-touch-targets"}. Anti-Patterns: Complex shadows + 3D effects + Muted colors + Low energy. Severity: HIGH.