Game Design Documents for ZX

Guidance for creating modular Game Design Documents tailored to Nethercore ZX console constraints. Supports three depth levels: Quick, Standard, and Comprehensive.

GDD Depth Levels

Quick GDD (1 page)

For rapid prototyping and game jams:

• High concept (2-3 sentences)
• Core mechanic description
• ZX constraints summary
• Asset list

Standard GDD (3-5 pages)

For pre-production and indie projects:

• Everything in Quick, plus:
• Detailed mechanics breakdown
• Level/world structure
• Memory budget allocation
• Control scheme
• Audio design notes

Comprehensive GDD (Full document)

For production and commercial projects:

• Everything in Standard, plus:
• Narrative design
• Character/enemy specifications
• Detailed art direction
• Multiplayer strategy
• Development milestones
• Technical challenges

GDD Creation Workflow

Step 1: Capture the Vision

Start with the core concept:

• One-sentence pitch ("A game where...")
• Target player experience
• Key differentiator
• Reference games (inspiration, not copying)

Step 2: Validate Against ZX Constraints

Before detailed design, confirm feasibility:

• Does the concept fit in 16 MB ROM?
• Is the game state small enough for rollback?
• Which render mode matches the art style?
• Can audio design work within 16 channels?

Step 3: Choose Depth Level

Select based on project needs:

• Quick: Proof of concept, game jam
• Standard: Indie development, small team
• Comprehensive: Commercial release, large scope

Step 4: Fill Template Sections

Work through template sections in order. Each section builds on previous ones.

Step 5: Review and Iterate

• Cross-check memory budgets
• Verify control scheme completeness
• Ensure multiplayer determinism (if applicable)

ZX-Specific Sections

Every ZX GDD should include these platform-specific sections:

Render Mode Rationale

Document the chosen render mode and why:

Render Mode: [0/1/2/3]
Rationale: [Why this mode fits the game]
Art Style Implications: [How this affects asset creation]

Memory Budget Summary

High-level ROM/RAM allocation:

ROM Budget (16 MB):
├── Code: X MB
├── Meshes: X MB
├── Textures: X MB
├── Audio: X MB
├── Animations: X MB
└── Remaining: X MB

RAM State Size: ~X KB (target < 100 KB for fast rollback)

Tick Rate Selection

Document the chosen tick rate:

Tick Rate: [24/30/60/120] fps
Rationale: [Why this rate for this game type]

Multiplayer Design (if applicable)

Player Count: [1-4]
Local/Online: [Local only / Online / Both]
Determinism Notes: [What systems need special care]
Input Handling: [How inputs are processed]

Document Location

Save GDDs to docs/design/:

project/
└── docs/
    └── design/
        ├── game-design.md       # Primary GDD
        ├── asset-specs.md       # Asset requirements
        └── technical-notes.md   # Implementation notes

Writing Guidelines

Be Specific

Instead of: "The game will have good graphics" Write: "Using Mode 2 (MR-Blinn-Phong) for realistic car materials, 512×512 diffuse textures per vehicle"

Include Constraints Early

Don't save technical limitations for the end. Weave them into each section:

• "The hub world supports 20 NPCs (within entity budget)"
• "Music loops are 30 seconds each (fits audio budget)"

Reference Procgen Opportunities

Mark assets suitable for procedural generation:

• "Background textures [PROCGEN: noise-based rock patterns]"
• "Ambient sounds [PROCGEN: synthesized atmosphere]"

Link Technical Tasks

Connect design decisions to implementation:

• "Character movement requires custom physics (see zx-dev: collision system)"
• "Menu system uses Mode 0 overlay (see zx-dev: render mode switching)"

Common Mistakes to Avoid

Scope Creep

ZX's constraints are features, not limitations. Respect them:

• 16 MB ROM is generous for focused games
• 4-player is maximum, not minimum
• 16 audio channels require planning

Vague Asset Descriptions

Instead of "various enemies," specify:

• Enemy count
• Animation states per enemy
• Estimated mesh/texture size

Ignoring Determinism

For multiplayer games, design for determinism from the start:

• No random without seeded random()
• No system time access
• No hash map iteration order dependencies

Additional Resources

Template Files

For ready-to-use GDD templates:

• references/gdd-template-quick.md — 1-page template
• references/gdd-template-standard.md — 3-5 page template
• references/gdd-template-comprehensive.md — Full template

Example Files

For filled-out examples:

• examples/gdd-example-fighting.md — Fighting game GDD
• examples/gdd-example-platformer.md — Platformer GDD

Integration with Plugin Suite

The GDD connects to other nethercore plugins:

→ zx-procgen

Asset specifications flow to procedural generation:

GDD: "Rock textures, 256×256, Mode 2 MRE workflow"
↓
Procgen: Generate tileable rock with MRE channels

→ zx-dev

Technical requirements flow to implementation:

GDD: "4-player fighting with 8 characters"
↓
zx-dev: Scaffold project with multiplayer, character system

The /plan-assets command extracts procgen-ready specs. The /design-game command generates complete GDDs.