Reverse Documentation

This skill analyzes existing implementation (code, prototypes, systems) and generates appropriate design or architecture documentation. Use this when:

You built a feature without writing a design doc first
You inherited a codebase without documentation
You prototyped a mechanic and need to formalize it
You need to document "why" behind existing code

Workflow

Phase 1: Parse Arguments

Format:

/reverse-document <type> <path>

Type options:

```
design
```
→ Generate a game design document (GDD section)
```
architecture
```
→ Generate an Architecture Decision Record (ADR)
```
concept
```
→ Generate a concept document from prototype

Path: Directory or file to analyze

```
src/gameplay/combat/
```
→ All combat-related code
```
src/core/event-system.cpp
```
→ Specific file
```
prototypes/stealth-mech/
```
→ Prototype directory

Examples:

bash

/reverse-document design src/gameplay/magic-system
/reverse-document architecture src/core/entity-component
/reverse-document concept prototypes/vehicle-combat

Phase 2: Analyze Implementation

Read and understand the code/prototype:

For design docs (GDD):

Identify mechanics, rules, formulas
Extract gameplay values (damage, cooldowns, ranges)
Find state machines, ability systems, progression
Detect edge cases handled in code
Map dependencies (what systems interact?)

For architecture docs (ADR):

Identify patterns (ECS, singleton, observer, etc.)
Understand technical decisions (threading, serialization, etc.)
Map dependencies and coupling
Assess performance characteristics
Find constraints and trade-offs

For concept docs (prototype analysis):

Identify core mechanic
Extract emergent gameplay patterns
Note what worked vs what didn't
Find technical feasibility insights
Document player fantasy / feel

Phase 3: Ask Clarifying Questions

DO NOT just describe the code. ASK about intent:

Design questions:

"I see a [resource] system that depletes during [activity]. Was this for:
- Pacing (prevent spam)?
- Resource management (strategic depth)?
- Or something else?"
"The [mechanic] seems central. Is this a core pillar, or supporting feature?"
"[Value] scales exponentially with [factor]. Intentional design, or needs rebalancing?"

Architecture questions:

"You're using a service locator pattern. Was this chosen for:
- Testability (mock dependencies)?
- Decoupling (reduce hard references)?
- Or inherited from existing code?"
"I see manual memory management instead of smart pointers. Performance requirement, or legacy?"

Concept questions:

"The prototype emphasizes stealth over combat. Is that the intended pillar?"
"Players seem to exploit the grappling hook for speed. Feature or bug?"

Phase 4: Present Findings

Before drafting, show what you discovered:

I've analyzed [path]/. Here's what I found:

MECHANICS IMPLEMENTED:
- [mechanic-a] with [property] (e.g. timing windows, cooldowns)
- [mechanic-b] (e.g. interaction between two states)
- [resource] system (depletes on [action], regens on [condition])
- [state] system (builds up, triggers [effect])

FORMULAS DISCOVERED:
- [Output] = [formula using discovered variables]
- [Secondary output] = [formula]

UNCLEAR INTENT AREAS:
1. [Resource] system — pacing or resource management?
2. [Mechanic] — core pillar or supporting feature?
3. [Value] scaling — intentional design or needs tuning?

Before I draft the design doc, could you clarify these points?

Wait for user to clarify intent before drafting.

Phase 5: Draft Document Using Template

Based on type, use appropriate template:

Type Template Output Path

Type	Template	Output Path
`design`	`templates/design-doc-from-implementation.md`	`design/gdd/[system-name].md`
`architecture`	`templates/architecture-doc-from-code.md`	`docs/architecture/[decision-name].md`
`concept`	`templates/concept-doc-from-prototype.md`	`prototypes/[name]/CONCEPT.md` or `design/concepts/[name].md`

design

templates/design-doc-from-implementation.md

design/gdd/[system-name].md

architecture

templates/architecture-doc-from-code.md

docs/architecture/[decision-name].md

concept

templates/concept-doc-from-prototype.md

prototypes/[name]/CONCEPT.md

design/concepts/[name].md

Draft structure:

Capture what exists (mechanics, patterns, implementation)
Document why it exists (intent clarified with user)
Identify what's missing (edge cases not handled, gaps in design)
Flag follow-up work (balance tuning, missing features)

Phase 6: Show Draft and Request Approval

Collaborative protocol:

I've drafted the [system-name] design doc based on your code and clarifications.

[Show key sections: Overview, Mechanics, Formulas, Design Intent]

ADDITIONS I MADE:
- Documented [mechanic] as "[intent]" per your clarification
- Added edge cases not in code (e.g., what if [resource] hits 0 mid-[action]?)
- Flagged balance concern: [scaling type] scaling at [boundary condition]

SECTIONS MARKED AS INCOMPLETE:
- "[System] interaction with [other-system]" (not fully implemented yet)
- "[Variant or feature]" (only [subset] implemented so far)

May I write this to design/gdd/[system-name].md?

Wait for approval. User may request changes before writing.

Phase 7: Write Document with Metadata

When approved, write the file with special markers:

markdown

---
status: reverse-documented
source: [path/]
date: [today]
verified-by: [User name]
---

# [System Name] Design

> **Note**: This document was reverse-engineered from the existing implementation.
> It captures current behavior and clarified design intent. Some sections may be
> incomplete where implementation is partial or intent was unclear.

[Rest of document...]

Phase 8: Flag Follow-Up Work

After writing, suggest next steps:

✅ Written to design/gdd/combat-system.md

FOLLOW-UP RECOMMENDED:
1. Run /balance-check on combat formulas (exponential scaling concern)
2. Create ADR for stamina system architecture decision
3. Implement missing edge cases:
   - Stamina depletion mid-combo behavior
   - Stagger state during dodge
4. Extend design doc when weapon variety is implemented

Would you like me to tackle any of these now?

Template Selection Logic

If analyzing...	Use template...	Because...
`src/gameplay/*`	design-doc-from-implementation.md	Gameplay mechanics → GDD
`src/core/` , `src/ai/`	architecture-doc-from-code.md	Core systems → ADR
`prototypes/*`	concept-doc-from-prototype.md	Experiments → concept doc
`src/networking/*`	architecture-doc-from-code.md	Technical systems → ADR
`src/ui/*`	design-doc-from-implementation.md	UI/UX → design spec

Example Session: Reverse-Document a System

User: /reverse-document design src/gameplay/[system]

Agent: I'll analyze your [system] implementation to create a design doc.
       [Reads code, discovers mechanics, formulas]

Agent: I've analyzed src/gameplay/[system]/. Here's what I found:
       [Shows mechanics, formulas, unclear areas]

       Before drafting, could you clarify:
       1. [Resource] system intent?
       2. Is [mechanic] a core pillar?
       3. [Value] scaling — intentional or needs tuning?

User: 1. [Resource] is for pacing, prevent [unwanted behavior]
      2. [Mechanic] is core — I want [design intent]
      3. Yeah, exponential is too much, should be linear

Agent: Perfect, that clarifies the vision. Let me draft the design doc.
       [Shows draft with clarified intent]

       May I write this to design/gdd/[system-name].md?

User: Yes, write it.

Agent: ✅ Written to design/gdd/[system-name].md
       ✅ Marked as [REVERSE-DOCUMENTED]
       ✅ Flagged [value] scaling for rebalancing

       Next steps:
       - Update [formula] to [corrected scaling]
       - Run /balance-check to validate [curve]
       - Document [mechanic] as core pillar in game-pillars.md

Collaborative Protocol

This skill follows the collaborative design principle:

Analyze First: Read code, understand implementation
Question Intent: Ask about "why", not just "what"
Present Findings: Show discoveries, highlight unclear areas
User Clarifies: Separate intent from accidents
Draft Document: Create doc based on reality + intent
Show Draft: Display key sections, explain additions
Get Approval: "May I write to [filepath]?" On approval: Verdict: COMPLETE — document generated. On decline: Verdict: BLOCKED — user declined write.
Flag Follow-Up: Suggest related work, don't auto-execute

Never assume intent. Always ask before documenting "why".

reverse-document

NPX Install

Tags

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