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skills/unity-ui-selector/SKILL.md

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+---
+name: Unity UI System Selector
+description: Guides selection between UGUI and UI Toolkit for projects. Use when choosing UI framework or migrating UI systems.
+---
+
+# Unity UI System Selector
+
+Helps you choose the appropriate UI system for your Unity project and provides implementation guidance for both UGUI and UI Toolkit.
+
+## Two UI Systems
+
+**UGUI (Legacy)** - GameObject-based (2014). Mature, works on all Unity versions, large community. Weaker: Complex UI performance, limited styling, no live reload.
+
+**UI Toolkit (Modern)** - Retained mode, web-inspired UXML/USS (2021.2+). Better performance, live reload, data-binding. Weaker: Requires 2021.2+, smaller community, limited 3D world-space UI.
+
+## Decision Framework
+
+**Use UGUI if:**
+- Unity < 2021.2
+- Simple UI (menus, HUD)
+- 3D world-space UI needed
+- Team knows UGUI well / tight deadline
+- Legacy project
+
+**Use UI Toolkit if:**
+- Unity 2021.2+ and new project (future-proof)
+- Complex/data-driven UI (inventory, skill trees)
+- Editor tools (inspectors, windows) - **strongly recommended**
+- Web dev background (HTML/CSS)
+- Large-scale UI (MMO, strategy games)
+
+When in doubt: For new projects on Unity 2021.2+, **UI Toolkit is recommended**.
+
+## Comparison
+
+| Feature | UGUI | UI Toolkit |
+|---------|------|-----------|
+| **Version** | 4.6+ | 2021.2+ |
+| **Performance** | Simple UIs | All UIs |
+| **Styling** | Inspector | CSS-like USS |
+| **Layout** | Manual/Groups | Flexbox-like |
+| **Editor Tools** | Good | Excellent |
+| **Runtime UI** | Excellent | Good |
+| **3D World UI** | Excellent | Limited |
+
+## Migration
+
+See [migration-guide.md](migration-guide.md) for UGUI → UI Toolkit migration strategy (3-4 months for medium projects).
+
+## UI System Support Matrix
+
+| Unity Version | UGUI | UI Toolkit (Editor) | UI Toolkit (Runtime) |
+|--------------|------|-------------------|---------------------|
+| 2019.4 LTS | ✅ Full | ✅ Basic | ❌ No |
+| 2020.3 LTS | ✅ Full | ✅ Good | ⚠️ Experimental |
+| 2021.3 LTS | ✅ Full | ✅ Excellent | ✅ Production |
+| 2022.3 LTS+ | ✅ Full | ✅ Primary | ✅ Full |
+
+## When to Use vs Other Components
+
+**Use this Skill when**: Choosing between UGUI and UI Toolkit, understanding UI system trade-offs, or planning UI migration
+
+**Use @unity-scripter agent when**: Implementing UI components, writing custom UI scripts, or converting UI code
+
+**Use @unity-architect agent when**: Designing complex UI architecture, planning UI data flow, or structuring large-scale UI systems
+
+**Use /unity:new-script command when**: Generating Editor scripts with UI Toolkit or UGUI templates
+
+## Related Skills
+
+- **unity-uitoolkit**: Assists with UI Toolkit implementation (UXML, USS, VisualElement API)
+- **unity-template-generator**: Generates Editor scripts using selected UI system
+- **unity-script-validator**: Validates UI code patterns