Architecture and API Documentation for Game Modules

Game Module Architecture and API Documentation

Documentation written not for show. Written when new programmer can't figure in three hours why EventBus.Publish<PlayerDiedEvent>() reloads scene in one place but only updates UI elsewhere. Or when author six months later doesn't remember why InventoryModule has internal 50-slot cache on top of main storage.

What makes game module documentation truly useful

Main mistake—documenting "what method does" when signature says it clearly. /// <summary>Adds item to inventory</summary> over AddItem(Item item) useless line. Valuable documentation answers three questions: why implemented exactly this way, what happens at boundary case and what interacts with this.

For game projects especially important: state documentation and dependencies. SaveSystem working via PlayerPrefs in Editor and cloud API in production—unintuitive behavior needing explicit description. Else developer writes test passing locally, failing on device.

Second layer—documentation of data flows between modules. In Unity with Zenject or VContainer dependencies injected, IDE not always hints where specific service came from. Architectural Decision Record (ADR) one page with dependency diagram saves hours on onboarding.

Documentation structure for game project

For modular game architecture, build documentation at several levels:

Architecture overview—diagram of modules and dependencies (PlantUML or Mermaid, embed directly in Markdown in Confluence/Notion). Mandatory: layers (Presentation, Domain, Infrastructure), dependency directions, what's Singleton, what created via factory.

Module cards—for each major module: purpose, public API, events emitted and subscribed to, initialization requirements (Awake/Start order), known limitations.

API Reference—generate from XML comments via DocFX or Doxygen. For C# Unity projects DocFX gives clean HTML with navigation. Configure autogeneration in CI: every push to main updates documentation on internal server.

Usage scenarios—concrete code examples for non-obvious cases. Not public void Initialize() with parameter description, but "how correctly initialize WeaponSystem in scene without PlayerController on startup."

For VR/AR projects add XR Interaction Flow section: event sequence from SelectEntered to SelectExited in XR Interaction Toolkit, controller button mapping, specifics of different HMDs (Quest vs Pico vs HTC Vive).

Tools and formats

DocFX—standard for C#/.NET projects, works well with Unity. Generates site from XML doc-comments + manual Markdown pages.

Doxygen—if project C++ (Unreal Engine). Supports diagrams via Graphviz.

Mermaid—for architecture diagrams directly in Markdown files. Renders in GitHub, GitLab, Notion, Confluence.

Confluence + structured templates—if team already on Atlassian stack. Create page templates for modules so documentation uniform.

Code comments via XML doc convention (C#): <summary>, <param>, <returns>, <exception>, <remarks>—last used for non-obvious behavior details.

How work structured

Audit existing codebase. Read code, identify non-obvious patterns, component connection points, non-standard solutions.

Interview developers. Ask about decisions not explained in code. Record as ADR.

Create documentation structure. Determine where documentation lives (Confluence, GitHub Wiki, separate DocFX site), what format for what tasks.

Write and mark up. Document modules by priority: most critical and opaque first.

Configure autogeneration. CI pipeline for API Reference updates on code changes.

Team review. Developers confirm correctness, identify gaps.

Cost is determined after codebase volume analysis and documentation format requirements.