setup-engine

When this skill is invoked:

1. Parse Arguments

Four modes:

• Full spec: /setup-engine godot 4.6 — engine and version provided
• Engine only: /setup-engine unity — engine provided, version will be looked up
• No args: /setup-engine — fully guided mode (engine recommendation + version)
• Refresh: /setup-engine refresh — update reference docs (see Section 10)
• Upgrade: /setup-engine upgrade [old-version] [new-version] — migrate to a new engine version (see Section 11)

2. Guided Mode (No Arguments)

If no engine is specified, run an interactive engine selection process:

Check for existing game concept

• Read design/gdd/game-concept.md if it exists — extract genre, scope, platform targets, art style, team size, and any engine recommendation from /brainstorm
• If no concept exists, inform the user:

  "No game concept found. Consider running /brainstorm first to discover what you want to build — it will also recommend an engine. Or tell me about your game and I can help you pick."

If the user wants to pick without a concept, ask in this order:

Question 1 — Prior experience (ask this first, always, via AskUserQuestion):

• Prompt: "Have you worked in any of these engines before?"
• Options: Godot / Unity / Unreal Engine 5 / Multiple — I'll explain / None of them
• If they pick a specific engine → recommend that engine. Prior experience outweighs all other factors. Confirm with them and skip the matrix.
• If "None" or "Multiple" → continue to the questions below.

Questions 2-6 — Decision matrix inputs (only if no prior engine experience):

Question 2 — Target platform (ask this second, always, via AskUserQuestion — platform eliminates or heavily weights engines before any other factor):

• Prompt: "What platforms are you targeting for this game?"
• Options: PC (Steam / Epic) / Mobile (iOS / Android) / Console / Web / Browser / Multiple platforms
• Platform rules that feed directly into the recommendation:
  • Mobile → Unity strongly preferred; Unreal is a poor fit; Godot is viable for simple mobile
  • Console → Unity or Unreal; Godot console support requires third-party publishers or significant extra work
  • Web → Godot exports cleanly to web; Unity WebGL is functional; Unreal has poor web support
  • PC only → all engines viable; other factors decide
  • Multiple → Unity is the most portable across PC/mobile/console

1. What kind of game? (2D, 3D, or both?)
2. Primary input method? (keyboard/mouse, gamepad, touch, or mixed?)
3. Team size and experience? (solo beginner, solo experienced, small team?)
4. Any strong language preferences? (GDScript, C#, C++, visual scripting?)
5. Budget for engine licensing? (free only, or commercial licenses OK?)

Produce a recommendation

Do NOT use a simple scoring matrix that eliminates engines. Instead, reason through the user's profile against the honest tradeoffs below, then present 1-2 recommendations with full context. Always end with the user choosing — never force a verdict.

Engine honest tradeoffs:

Godot 4

• Genuine strengths: 2D (best in class), stylized/indie 3D, rapid iteration, free forever (MIT), open source, gentlest learning curve, best for solo devs who want full control
• Real limitations: 3D ecosystem is thin compared to Unity/Unreal (fewer tutorials, assets, community answers for 3D-specific problems); large open-world 3D is very hard and largely untested in Godot; console export requires third-party publishers or significant extra work; smaller professional job market
• Licensing reality: Truly free with no revenue thresholds ever. MIT license means you own everything.
• Best fit: 2D games of any scope; stylized/atmospheric 3D; contained 3D worlds (not open-world); first game projects where learning curve matters; projects where budget is a hard constraint at any scale

Unity

• Genuine strengths: Industry standard for mid-scope 3D and mobile; massive asset store and tutorial ecosystem; C# is a professional language; best console certification support for indie; strong community for almost every genre
• Real limitations: Licensing controversy in 2023 damaged trust (runtime fee was proposed then walked back — the risk of policy changes remains real); C# has a steeper initial curve than GDScript; heavier editor than Godot for simple projects
• Licensing reality: Free under $200K revenue AND 200K installs (Unity Personal/Plus). Only becomes costly if the game is genuinely successful — most indie games never hit this threshold. The 2023 controversy is worth knowing about but the actual current terms are reasonable for most indie developers.
• Best fit: Mobile games; mid-scope 3D; games targeting console; developers with C# background; projects needing large asset store; teams of 2-5

Unreal Engine 5

• Genuine strengths: Best-in-class 3D visuals (Lumen, Nanite, Chaos physics); industry standard for AAA and photorealistic 3D; large open-world support is mature and production-tested; Blueprint visual scripting lowers C++ barrier; strong for games targeting high-end PC or console
• Real limitations: Steepest learning curve; heaviest editor (slow compile times, large project sizes); overkill for stylized/2D/small-scope games; C++ is genuinely hard; not suitable for mobile or web; 5% royalty past $1M gross revenue
• Licensing reality: 5% royalty only applies AFTER $1M gross revenue per title. For a first game or any game that doesn't reach $1M, it costs nothing. This threshold is high enough that most indie developers will never pay it.
• Best fit: AAA-quality 3D; large open-world games; photorealistic visuals; developers with C++ experience or willing to use Blueprint; games targeting high-end PC/console where visual fidelity is a core selling point

Genre-specific guidance (factor this into the recommendation):

• 2D any style → Godot strongly preferred
• 3D stylized / atmospheric / contained world → Godot viable, Unity solid alternative
• 3D open world (large, seamless) → Unity or Unreal; Godot is not production-proven for this
• 3D photorealistic / AAA-quality → Unreal
• Mobile-first → Unity strongly preferred
• Console-first → Unity or Unreal; Godot console support requires extra work
• Horror / narrative / walking sim → any engine; match to art style and team experience
• Action RPG / Soulslike → Unity or Unreal for 3D; community support and assets matter here
• Platformer 2D → Godot
• Strategy / top-down / RTS → Godot or Unity depending on 2D vs 3D

Recommendation format:

1. Show a comparison table with the user's specific factors as rows
2. Give a primary recommendation with honest reasoning
3. Name the best alternative and when to choose it instead
4. Explicitly state: "This is a starting point, not a verdict — you can always migrate engines, and many developers switch between projects."
5. Use AskUserQuestion to confirm: "Does this recommendation feel right, or would you like to explore a different engine?"
   • Options: [Primary engine] (Recommended) / [Alternative engine] / [Third engine] / Explore further / Type something

If the user picks "Explore further": Use AskUserQuestion with concept-specific deep-dive topics. Always generate these options from the user's actual concept — do not use generic options. Always include at minimum:

• The primary engine's specific limitations for this concept (e.g., "How far can Godot 3D actually go for [genre]?")
• The alternative engine's specific tradeoffs for this concept
• Language choice impact on this concept's technical challenges
• Any concept-specific technical concern (e.g., adaptive audio, open-world streaming, multiplayer netcode)

The user can select multiple topics. Answer each selected topic in depth before returning to the engine confirmation question.

3. Look Up Current Version

Once the engine is chosen:

• If version was provided, use it
• If no version provided, use WebSearch to find the latest stable release:
  • Search: "[engine] latest stable version [current year]"
  • Confirm with the user: "The latest stable [engine] is [version]. Use this?"

4. Update CLAUDE.md Technology Stack

Language Selection (Godot only)

If Godot was chosen, ask the user which language to use before showing the proposed Technology Stack:

"Godot supports two primary languages:

A) GDScript — Python-like, Godot-native, fastest iteration. Best for beginners, solo devs, and teams coming from Python or Lua. B) C# — .NET 8+, familiar to Unity developers, stronger IDE tooling (Rider / Visual Studio), slight performance advantage on heavy logic. C) Both — GDScript for gameplay/UI scripting, C# for performance-critical systems. Advanced setup — requires .NET SDK alongside Godot.

Which will this project primarily use?"

Record the choice. It determines the CLAUDE.md template, naming conventions, specialist routing, and which agent is spawned for code files throughout the project.

Read CLAUDE.md and show the user the proposed Technology Stack changes. Ask: "May I write these engine settings to CLAUDE.md?"

Wait for confirmation before making any edits.

Update the Technology Stack section, replacing the [CHOOSE] placeholders with the actual values:

For Godot — use the template matching the language chosen above. See Appendix A at the bottom of this skill for all three variants (GDScript, C#, Both).

For Unity:

- **Engine**: Unity [version]
- **Language**: C#
- **Build System**: Unity Build Pipeline
- **Asset Pipeline**: Unity Asset Import Pipeline + Addressables

For Unreal:

- **Engine**: Unreal Engine [version]
- **Language**: C++ (primary), Blueprint (gameplay prototyping)
- **Build System**: Unreal Build Tool (UBT)
- **Asset Pipeline**: Unreal Content Pipeline

5. Populate Technical Preferences

After updating CLAUDE.md, create or update .claude/docs/technical-preferences.md with engine-appropriate defaults. Read the existing template first, then fill in:

Engine & Language Section

• Fill from the engine choice made in step 4

Naming Conventions (engine defaults)

For Godot — see Appendix A for GDScript, C#, and Both variants.

For Unity (C#):

• Classes: PascalCase (e.g., PlayerController)
• Public fields/properties: PascalCase (e.g., MoveSpeed)
• Private fields: _camelCase (e.g., _moveSpeed)
• Methods: PascalCase (e.g., TakeDamage())
• Files: PascalCase matching class (e.g., PlayerController.cs)
• Constants: PascalCase or UPPER_SNAKE_CASE

For Unreal (C++):

• Classes: Prefixed PascalCase (A for Actor, U for UObject, F for struct)
• Variables: PascalCase (e.g., MoveSpeed)
• Functions: PascalCase (e.g., TakeDamage())
• Booleans: b prefix (e.g., bIsAlive)
• Files: Match class without prefix (e.g., PlayerController.h)

Input & Platform Section

Populate ## Input & Platform using the answers gathered in Section 2 (or extracted from the game concept). Derive the values using this mapping:

For Primary Input, use the dominant input for the game genre:

• Action/RPG/platformer targeting console → Gamepad
• Strategy/point-and-click/RTS → Keyboard/Mouse
• Mobile game → Touch
• Cross-platform → ask the user

Present the derived values and ask the user to confirm or adjust before writing.

Example filled section:

## Input & Platform
- **Target Platforms**: PC, Console
- **Input Methods**: Keyboard/Mouse, Gamepad
- **Primary Input**: Gamepad
- **Gamepad Support**: Full
- **Touch Support**: None
- **Platform Notes**: All UI must support d-pad navigation. No hover-only interactions.

Remaining Sections

• Performance Budgets: Use AskUserQuestion:
  • Prompt: "Should I set default performance budgets now, or leave them for later?"
  • Options: [A] Set defaults now (60fps, 16.6ms frame budget, engine-appropriate draw call limit) / [B] Leave as [TO BE CONFIGURED] — I'll set these when I know my target hardware
  • If [A]: populate with the suggested defaults. If [B]: leave as placeholder.
• Testing: Suggest engine-appropriate framework (GUT for Godot, NUnit for Unity, etc.) — ask before adding.
• Forbidden Patterns: Leave as placeholder — do NOT pre-populate.
• Allowed Libraries: Leave as placeholder — do NOT pre-populate dependencies the project does not currently need. Only add a library here when it is actively being integrated, not speculatively.

Guardrail: Never add speculative dependencies to Allowed Libraries. For example, do NOT add GodotSteam unless Steam integration is actively beginning in this session. Post-launch integrations should be added to Allowed Libraries when that work begins, not during engine setup.

Engine Specialists Routing

Also populate the ## Engine Specialists section in technical-preferences.md with the correct routing for the chosen engine:

For Godot — see Appendix A for the routing table matching the language chosen.

For Unity:

## Engine Specialists
- **Primary**: unity-specialist
- **Language/Code Specialist**: unity-specialist (C# review — primary covers it)
- **Shader Specialist**: unity-shader-specialist (Shader Graph, HLSL, URP/HDRP materials)
- **UI Specialist**: unity-ui-specialist (UI Toolkit UXML/USS, UGUI Canvas, runtime UI)
- **Additional Specialists**: unity-dots-specialist (ECS, Jobs system, Burst compiler), unity-addressables-specialist (asset loading, memory management, content catalogs)
- **Routing Notes**: Invoke primary for architecture and general C# code review. Invoke DOTS specialist for any ECS/Jobs/Burst code. Invoke shader specialist for rendering and visual effects. Invoke UI specialist for all interface implementation. Invoke Addressables specialist for asset management systems.

### File Extension Routing

| File Extension / Type | Specialist to Spawn |
|-----------------------|---------------------|
| Game code (.cs files) | unity-specialist |
| Shader / material files (.shader, .shadergraph, .mat) | unity-shader-specialist |
| UI / screen files (.uxml, .uss, Canvas prefabs) | unity-ui-specialist |
| Scene / prefab / level files (.unity, .prefab) | unity-specialist |
| Native extension / plugin files (.dll, native plugins) | unity-specialist |
| General architecture review | unity-specialist |

For Unreal:

## Engine Specialists
- **Primary**: unreal-specialist
- **Language/Code Specialist**: ue-blueprint-specialist (Blueprint graphs) or unreal-specialist (C++)
- **Shader Specialist**: unreal-specialist (no dedicated shader specialist — primary covers materials)
- **UI Specialist**: ue-umg-specialist (UMG widgets, CommonUI, input routing, widget styling)
- **Additional Specialists**: ue-gas-specialist (Gameplay Ability System, attributes, gameplay effects), ue-replication-specialist (property replication, RPCs, client prediction, netcode)
- **Routing Notes**: Invoke primary for C++ architecture and broad engine decisions. Invoke Blueprint specialist for Blueprint graph architecture and BP/C++ boundary design. Invoke GAS specialist for all ability and attribute code. Invoke replication specialist for any multiplayer or networked systems. Invoke UMG specialist for all UI implementation.

### File Extension Routing

| File Extension / Type | Specialist to Spawn |
|-----------------------|---------------------|
| Game code (.cpp, .h files) | unreal-specialist |
| Shader / material files (.usf, .ush, Material assets) | unreal-specialist |
| UI / screen files (.umg, UMG Widget Blueprints) | ue-umg-specialist |
| Scene / prefab / level files (.umap, .uasset) | unreal-specialist |
| Native extension / plugin files (Plugin .uplugin, modules) | unreal-specialist |
| Blueprint graphs (.uasset BP classes) | ue-blueprint-specialist |
| General architecture review | unreal-specialist |

Collaborative Step

Present the filled-in preferences to the user. For Godot, include the chosen language and note where the full naming conventions and routing tables live:

"Here are the default technical preferences for [engine] ([language if Godot]). The naming conventions and specialist routing are in Appendix A of this skill — I'll apply the [GDScript/C#/Both] variant. Want to customize any of these, or shall I save the defaults?"

For all other engines, present the defaults directly without referencing the appendix.

Wait for approval before writing the file.

6. Determine Knowledge Gap

Check whether the engine version is likely beyond the LLM's training data.

Known approximate coverage (update this as models change):

• LLM knowledge cutoff: May 2025
• Godot: training data likely covers up to ~4.3
• Unity: training data likely covers up to ~2023.x / early 6000.x
• Unreal: training data likely covers up to ~5.3 / early 5.4

Compare the user's chosen version against these baselines:

• Within training data → LOW RISK — reference docs optional but recommended
• Near the edge → MEDIUM RISK — reference docs recommended
• Beyond training data → HIGH RISK — reference docs required

Inform the user which category they're in and why.

7. Populate Engine Reference Docs

If WITHIN training data (LOW RISK):

Create a minimal docs/engine-reference/<engine>/VERSION.md:

# [Engine] — Version Reference

| Field | Value |
|-------|-------|
| **Engine Version** | [version] |
| **Project Pinned** | [today's date] |
| **LLM Knowledge Cutoff** | May 2025 |
| **Risk Level** | LOW — version is within LLM training data |

## Note

This engine version is within the LLM's training data. Engine reference
docs are optional but can be added later if agents suggest incorrect APIs.

Run `/setup-engine refresh` to populate full reference docs at any time.

Do NOT create breaking-changes.md, deprecated-apis.md, etc. — they would add context cost with minimal value.

If BEYOND training data (MEDIUM or HIGH RISK):

Create the full reference doc set by searching the web:

1. Search for the official migration/upgrade guide:

   • "[engine] [old version] to [new version] migration guide"
   • "[engine] [version] breaking changes"
   • "[engine] [version] changelog"
   • "[engine] [version] deprecated API"

2. Fetch and extract from official documentation:

   • Breaking changes between each version from the training cutoff to current
   • Deprecated APIs with replacements
   • New features and best practices

Ask: "May I create the engine reference docs under docs/engine-reference/<engine>/?"

Wait for confirmation before writing any files.

1. Create the full reference directory:

   docs/engine-reference/<engine>/
   ├── VERSION.md              # Version pin + knowledge gap analysis
   ├── breaking-changes.md     # Version-by-version breaking changes
   ├── deprecated-apis.md      # "Don't use X → Use Y" tables
   ├── current-best-practices.md  # New practices since training cutoff
   └── modules/                # Per-subsystem references (create as needed)
   

2. Populate each file using real data from the web searches, following the format established in existing reference docs. Every file must have a "Last verified: [date]" header.

3. For module files: Only create modules for subsystems where significant changes occurred. Don't create empty or minimal module files.

8. Update CLAUDE.md Import

Ask: "May I update the @ import in CLAUDE.md to point to the new engine reference?"

Wait for confirmation, then update the @ import under "Engine Version Reference" to point to the correct engine:

## Engine Version Reference

@docs/engine-reference/<engine>/VERSION.md

If the previous import pointed to a different engine (e.g., switching from Godot to Unity), update it.

9. Update Agent Instructions

Ask: "May I add a Version Awareness section to the engine specialist agent files?" before making any edits.

For the chosen engine's specialist agents, verify they have a "Version Awareness" section. If not, add one following the pattern in the existing Godot specialist agents.

The section should instruct the agent to:

1. Read docs/engine-reference/<engine>/VERSION.md
2. Check deprecated APIs before suggesting code
3. Check breaking changes for relevant version transitions
4. Use WebSearch to verify uncertain APIs

10. Refresh Subcommand

If invoked as /setup-engine refresh:

1. Read the existing docs/engine-reference/<engine>/VERSION.md to get the current engine and version
2. Use WebSearch to check for:
   • New engine releases since last verification
   • Updated migration guides
   • Newly deprecated APIs
3. Update all reference docs with new findings
4. Update "Last verified" dates on all modified files
5. Report what changed

11. Upgrade Subcommand

If invoked as /setup-engine upgrade [old-version] [new-version]:

Step 1 — Read Current Version State

Read docs/engine-reference/<engine>/VERSION.md to confirm the current pinned version, risk level, and any migration note URLs already recorded. If old-version was not provided as an argument, use the pinned version from this file.

Step 2 — Fetch Migration Guide

Use WebSearch and WebFetch to locate the official migration guide between old-version and new-version:

• Search: "[engine] [old-version] to [new-version] migration guide"
• Search: "[engine] [new-version] breaking changes changelog"
• Fetch the migration guide URL from VERSION.md if one is already recorded, or use the URL found via search.

Extract: renamed APIs, removed APIs, changed defaults, behavior changes, and any "must migrate" items.

Step 3 — Pre-Upgrade Audit

Scan src/ for code that uses APIs known to be deprecated or changed in the target version:

• Use Grep to search for deprecated API names extracted from the migration guide (e.g., old function names, removed node types, changed property names)
• List each file that matches, with the specific API reference found

Present the audit results as a table:

Pre-Upgrade Audit: [engine] [old-version] → [new-version]
==========================================================

Files requiring changes:
  File                              | Deprecated API Found       | Effort
  --------------------------------- | -------------------------- | ------
  src/gameplay/player_movement.gd   | old_api_name               | Low
  src/ui/hud.gd                     | removed_node_type          | Medium

Breaking changes to watch for:
  - [change description from migration guide]
  - [change description from migration guide]

Recommended migration order (dependency-sorted):
  1. [system/layer with fewest dependencies first]
  2. [next system]
  ...

If no deprecated APIs are found in src/, report: "No deprecated API usage found in src/ — upgrade may be low-risk."

Step 4 — Confirm Before Updating

Ask the user before making any changes:

"Pre-upgrade audit complete. Found [N] files using deprecated APIs. Proceed with upgrading VERSION.md to [new-version]? (This will update t