--- name: Game Design System slug: game-design-system-2 category: Writing description: "Game Design System guides section-by-section authoring of a single game system's GDD, gathering context from existing docs, cross-referencing dependencies, and writing incrementally to file. Use it to design game mechanics with consistency against a systems index and registry." github: "https://github.com/Donchitos/Claude-Code-Game-Studios/tree/main/.claude/skills/design-system" language: Shell stars: 23864 forks: 3411 install: "npx degit https://github.com/Donchitos/Claude-Code-Game-Studios/tree/main/.claude/skills/design-system ~/.claude/skills/design-system" installs_to: ~/.claude/skills/design-system source_path: .claude/skills/design-system/SKILL.md collection_size: 25 category_size: 1012 collection_url: "https://dirskills.com/collections/Donchitos/Claude-Code-Game-Studios" added: 2026-08-14T07:12:30.654Z last_synced: 2026-08-14T07:12:30.654Z canonical_url: "https://dirskills.com/skills/game-design-system-2" --- # Game Design System Game Design System guides section-by-section authoring of a single game system's GDD, gathering context from existing docs, cross-referencing dependencies, and writing incrementally to file. Use it to design game mechanics with consistency against a systems index and registry. **Install:** ```bash npx degit https://github.com/Donchitos/Claude-Code-Game-Studios/tree/main/.claude/skills/design-system ~/.claude/skills/design-system ``` ## README When this skill is invoked: ## 1. Parse Arguments & Validate Resolve the review mode (once, store for all gate spawns this run): 1. If `--review [full|lean|solo]` was passed → use that 2. Else read `production/review-mode.txt` → use that value 3. Else → default to `lean` See `.claude/docs/director-gates.md` for the full check pattern. A system name or retrofit path is **required**. If missing: 1. Check if `design/gdd/systems-index.md` exists. 2. If it exists: read it, find the highest-priority system with status "Not Started" or equivalent, and use `AskUserQuestion`: - Prompt: "The next system in your design order is **[system-name]** ([priority] | [layer]). Start designing it?" - Options: `[A] Yes — design [system-name]` / `[B] Pick a different system` / `[C] Stop here` - If [A]: proceed with that system name. If [B]: ask which system to design (plain text). If [C]: exit. 3. If no systems index exists, fail with: > "Usage: `/design-system ` — e.g., `/design-system movement` > Or to fill gaps in an existing GDD: `/design-system retrofit design/gdd/[system-name].md` > No systems index found. Run `/map-systems` first to map your systems and get the design order." **Detect retrofit mode:** If the argument starts with `retrofit` or the argument is a file path to an existing `.md` file in `design/gdd/`, enter **retrofit mode**: 1. Read the existing GDD file. 2. Identify which of the 8 required sections are present (scan for section headings). Required sections: Overview, Player Fantasy, Detailed Design/Rules, Formulas, Edge Cases, Dependencies, Tuning Knobs, Acceptance Criteria. 3. Identify which sections contain only placeholder text (`[To be designed]` or equivalent — blank, a single line, or obviously incomplete). 4. Present to the user before doing anything: ``` ## Retrofit: [System Name] File: design/gdd/[filename].md Sections already written (will not be touched): ✓ [section name] ✓ [section name] Missing or incomplete sections (will be authored): ✗ [section name] — missing ✗ [section name] — placeholder only ``` 5. Ask: "Shall I fill the [N] missing sections? I will not modify any existing content." 6. If yes: proceed to **Phase 2 (Gather Context)** as normal, but in **Phase 3** skip creating the skeleton (file already exists) and in **Phase 4** skip sections that are already complete. Only run the section cycle for missing/ incomplete sections. 7. **Never overwrite existing section content.** Use Edit tool to replace only `[To be designed]` placeholders or empty section bodies. If NOT in retrofit mode, normalize the system name to kebab-case for the filename (e.g., "combat system" becomes `combat-system`). --- ## 2. Gather Context (Read Phase) Read all relevant context **before** asking the user anything. This is the skill's primary advantage over ad-hoc design — it arrives informed. ### 2a: Required Reads - **Game concept**: Read `design/gdd/game-concept.md` — fail if missing: > "No game concept found. Run `/brainstorm` first." - **Systems index**: Read `design/gdd/systems-index.md` — fail if missing: > "No systems index found. Run `/map-systems` first to map your systems." - **Target system**: Find the system in the index. If not listed, warn: > "[system-name] is not in the systems index. Would you like to add it, or > design it as an off-index system?" - **Entity registry**: Read `design/registry/entities.yaml` if it exists. Extract all entries referenced by or relevant to this system (grep `referenced_by.*[system-name]` and `source.*[system-name]`). Hold these in context as **known facts** — values that other GDDs have already established and this GDD must not contradict. - **Reflexion log**: Read `docs/consistency-failures.md` if it exists. Extract entries whose Domain matches this system's category. These are recurring conflict patterns — present them under "Past failure patterns" in the Phase 2d context summary so the user knows where mistakes have occurred before in this domain. ### 2b: Dependency Reads From the systems index, identify: - **Upstream dependencies**: Systems this one depends on. Read their GDDs if they exist (these contain decisions this system must respect). - **Downstream dependents**: Systems that depend on this one. Read their GDDs if they exist (these contain expectations this system must satisfy). For each dependency GDD that exists, extract and hold in context: - Key interfaces (what data flows between the systems) - Formulas that reference this system's outputs - Edge cases that assume this system's behavior - Tuning knobs that feed into this system ### 2c: Optional Reads - **Game pillars**: Read `design/gdd/game-pillars.md` if it exists - **Existing GDD**: Read `design/gdd/[system-name].md` if it exists (resume, don't restart from scratch) - **Related GDDs**: Glob `design/gdd/*.md` and read any that are thematically related (e.g., if designing a system that overlaps with another in scope, read the related GDD even if it's not a formal dependency) ### 2d: Present Context Summary Before starting design work, present a brief summary to the user: > **Designing: [System Name]** > - Priority: [from index] | Layer: [from index] > - Depends on: [list, noting which have GDDs vs. undesigned] > - Depended on by: [list, noting which have GDDs vs. undesigned] > - Existing decisions to respect: [key constraints from dependency GDDs] > - Pillar alignment: [which pillar(s) this system primarily serves] > - **Known cross-system facts (from registry):** > - [entity_name]: [attribute]=[value], [attribute]=[value] (owned by [source GDD]) > - [item_name]: [attribute]=[value], [attribute]=[value] (owned by [source GDD]) > - [formula_name]: variables=[list], output=[min–max] (owned by [source GDD]) > - [constant_name]: [value] [unit] (owned by [source GDD]) > *(These values are locked — if this GDD needs different values, surface > the conflict before writing. Do not silently use different numbers.)* > > If no registry entries are relevant: omit the "Known cross-system facts" section. If any upstream dependencies are undesigned, warn: > "[dependency] doesn't have a GDD yet. We'll need to make assumptions about > its interface. Consider designing it first, or we can define the expected > contract and flag it as provisional." ### 2e: Technical Feasibility Pre-Check Before asking the user to begin designing, load engine context and surface any constraints or knowledge gaps that will shape the design. **Step 1 — Determine the engine domain for this system:** Map the system's category (from systems-index.md) to an engine domain: | System Category | Engine Domain | |----------------|--------------| | Combat, physics, collision | Physics | | Rendering, visual effects, shaders | Rendering | | UI, HUD, menus | UI | | Audio, sound, music | Audio | | AI, pathfinding, behavior trees | Navigation / Scripting | | Animation, IK, rigs | Animation | | Networking, multiplayer, sync | Networking | | Input, controls, keybinding | Input | | Save/load, persistence, data | Core | | Dialogue, quests, narrative | Scripting | **Step 2 — Read engine context (if available):** - Read `.claude/docs/technical-preferences.md` to identify the engine and version - If engine is configured, read `docs/engine-reference/[engine]/VERSION.md` - Read `docs/engine-reference/[engine]/modules/[domain].md` if it exists - Read `docs/engine-reference/[engine]/breaking-changes.md` for domain-relevant entries - Glob `docs/architecture/adr-*.md` and read any ADRs whose domain matches (check the Engine Compatibility table's "Domain" field) **Step 3 — Present the Feasibility Brief:** If engine reference docs exist, present before starting design: ``` ## Technical Feasibility Brief: [System Name] Engine: [name + version] Domain: [domain] ### Known Engine Capabilities (verified for [version]) - [capability relevant to this system] - [capability 2] ### Engine Constraints That Will Shape This Design - [constraint from engine-reference or existing ADR] ### Knowledge Gaps (verify before committing to these) - [post-cutoff feature this design might rely on — mark HIGH/MEDIUM risk] ### Existing ADRs That Constrain This System - ADR-XXXX: [decision summary] — means [implication for this GDD] (or "None yet") ``` If no engine reference docs exist (engine not yet configured), show a short note: > "No engine configured yet — skipping technical feasibility check. Run > `/setup-engine` before moving to architecture if you haven't already." **Step 4 — Ask before proceeding:** Use `AskUserQuestion`: - "Any constraints to add before we begin, or shall we proceed with these noted?" - Options: "Proceed with these noted", "Add a constraint first", "I need to check the engine docs — pause here" --- Use `AskUserQuestion`: - "Ready to start designing [system-name]?" - Options: "Yes, let's go", "Show me more context first", "Design a dependency first" --- ## 3. Create File Skeleton Once the user confirms, **immediately** create the GDD file with empty section headers. This ensures incremental writes have a target. Use the template structure from `.claude/docs/templates/game-design-document.md`: ```markdown # [System Name] > **Status**: In Design > **Author**: [user + agents] > **Last Updated**: [today's date] > **Implements Pillar**: [from context] ## Overview [To be designed] ## Player Fantasy [To be designed] ## Detailed Design ### Core Rules [To be designed] ### States and Transitions [To be designed] ### Interactions with Other Systems [To be designed] ## Formulas [To be designed] ## Edge Cases [To be designed] ## Dependencies [To be designed] ## Tuning Knobs [To be designed] ## Visual/Audio Requirements [To be designed] ## UI Requirements [To be designed] ## Acceptance Criteria [To be designed] ## Open Questions [To be designed] ``` Ask: "May I create the skeleton file at `design/gdd/[system-name].md`?" If the user declines: Stop with the following message: > "Verdict: **BLOCKED** — skeleton creation declined. The design session cannot proceed without the skeleton file, as all subsequent phases use it as the base. Re-run `/design-system [system]` when ready to create the file." Do not proceed to Section A. After writing, update `production/session-state/active.md`: - Use Glob to check if the file exists. - If it **does not exist**: use the **Write** tool to create it. Never attempt Edit on a file that may not exist. - If it **already exists**: use the **Edit** tool to update the relevant fields. File content: - Task: Designing [system-name] GDD - Current section: Starting (skeleton created) - File: design/gdd/[system-name].md --- ## 4. Section-by-Section Design Walk through each section in order. For **each section**, follow this cycle: ### The Section Cycle ``` Context -> Questions -> Options -> Decision -> Draft -> Approval -> Write ``` 1. **Context**: State what this section needs to contain, and surface any relevant decisions from dependency GDDs that constrain it. 2. **Questions**: Ask clarifying questions specific to this section. Use `AskUserQuestion` for constrained questions, conversational text for open-ended exploration. 3. **Options**: Where the section involves design choices (not just documentation), present 2-4 approaches with pros/cons. Explain reasoning in conversation text, then use `AskUserQuestion` to capture the decision. 4. **Decision**: User picks an approach or provides custom direction. 5. **Draft**: Write the section content in conversation text for review. Flag any provisional assumptions about undesigned dependencies. 6. **Approval**: Immediately after the draft — in the SAME response — use `AskUserQuestion`. **NEVER use plain text. NEVER skip this step.** - Prompt: "Approve the [Section Name] section?" - Options: `[A] Approve — write it to file` / `[B] Make changes — describe what to fix` / `[C] Start over` **The draft and the approval widget MUST appear together in one response. If the draft appears without the widget, the user is left at a blank prompt with no path forward — this is a protocol violation.** 7. **Write**: Use the Edit tool to replace the placeholder with the approved content. **CRITICAL**: Always include the section heading in the `old_string` to ensure uniqueness — never match `[To be designed]` alone, as multiple sections use the same placeholder and the Edit tool requires a unique match. Use this pattern: ``` old_string: "## [Section Name]\n\n[To be designed]" new_string: "## [Section Name]\n\n[approved content]" ``` Confirm the write. 8. **Registry conflict check** (Sections C and D only — Detailed Design and Formulas): After writing, scan the section content for entity names, item names, formula names, and numeric constants that appear in the registry. For each match: - Compare the value just written against the registry entry. - If they differ: **surface the conflict immediately** before starting the next section. Do not continue silently. > "Registry conflict: [name] is registered in [source GDD] as [registry_value]. > This section just wrote [new_value]. Which is correct?" - If new (not in registry): flag it as a candidate for registry registration (will be handled in Phase 5). After writing each section, update `production/session-state/active.md` with the completed section name. Use Glob to check if the file exists — use Write to create it if absent, Edit to update it if present. ### Section-Specific Guidance Each section has unique design considerations and may benefit from specialist agents: --- ### Section A: Overview **Goal**: One paragraph a stranger could read and understand. **Derive recommended options before building the widget**: Read the system's category and layer from the systems index (already in context from Phase 2), then determine the recommended option for each tab: - **Framing tab**: Foundation/Infrastructure layer → `[A]` recommended. Player-facing categories (Combat, UI, Dialogue, Character, Animation, Visual Effects, Audio) → `[C] Both` recommended. - **ADR ref tab**: Glob `docs/architecture/adr-*.md` and grep for the system name in the GDD Requirements section of any ADR. If a matching ADR is found → `[A] Yes — cite the ADR` recommended. If none found → `[B] No` recommended. - **Fantasy tab**: Foundation/Infrastructure layer → `[B] No` recommended. All other categories → `[A] Yes` recommended. Append `(Recommended)` to the appropriate option text in each tab. **Framing questions (ask BEFORE drafting)**: Use `AskUserQuestion` with a multi-tab widget: - Tab "Framing" — "How should the overview frame this system?" Options: `[A] As a data/infrastructure layer (technical framing)` / `[B] Through its player-facing effect (design framing)` / `[C] Both — describe the data layer and its player impact` - Tab "ADR ref" — "Should the overview reference the existing ADR for this system?" Options: `[A] Yes — cite the ADR for implementation details` / `[B] No — keep the GDD at pure design level` - Tab "Fantasy" — "Does this system have a player fantasy worth stating?" Options: `[A] Yes — players feel it directly` / `[B] No — pure infrastructure, players feel what it enables` Use the user's answers to shape the draft. Do NOT answer these questions yourself and auto-draft. **Questions to ask**: - What is this system in one sentence? - How does a player interact with it? (active/passive/automatic) - Why does this system exist — what would the game lose without it? **Cross-reference**: Check that the description aligns with how the systems index describes it. Flag discrepancies. **Design vs. implementation boundary**: Overview questions must stay at the behavior level — what the system *does*, not *how it is built*. If implementation questions arise during the Overview (e.g., "Should this use an Autoload singleton or a signal bus?"), note them as "→ becomes an ADR" and move on. Implementation patterns belong in `/architecture-decision`, not the GDD. The GDD describes behavior; the ADR describes the technical approach used to achieve it. --- ### Section B: Player Fantasy **Goal**: The emotional target — what the player should *feel*. **Derive recommended option before building the widget**: Read the system's category and layer from Phase 2 context: - Player-facing categories (Combat, UI, Dialogue, Character, Animation, Audio, Level/World) → `[A] Direct` recommended - Foundation/Infrastructure layer → `[B] Indirect` recommended - Mixed categories (Camera/input, Economy, AI with visible player effects) → `[C] Both` recommended Append `(Recommended)` to the appropriate option text. **Framing question (ask BEFORE drafting)**: Use `AskUserQuestion`: - Prompt: "Is this system something the player engages with directly, or infrastructure they experience indirectly?" - Options: `[A] Direct — player actively uses or feels this system` / `[B] Indirect — player experiences the effects, not the system` / `[C] Both — has a direct interaction layer and infrastructure beneath it` Use the answer to frame the Player Fantasy section appropriately. Do NOT assume the answer. **Questions to ask**: - What emotion or power fantasy does this serve? - What reference games nail this feeling? What specifically creates it? - Is this a "system you love engaging with" or "infrastructure you don't notice"? **Cross-reference**: Must align with the game pillars. If the system serves a pillar, quote the relevant pillar text. **Review mode check** (apply before spawning): - `solo` → skip this agent spawn. Draft the section without the specialist. Add a note: "`creative-director` not consulted — Solo mode. Review manually before production." - `lean` → skip unless this is a section with HIGH implementation risk (Sections D and H only). For other sections, draft without the agent. - `full` → spawn as described below. **Agent delegation (MANDATORY)**: After the framing answer is given but before drafting, spawn `creative-director` via Task: - Provide: system name, framing answer (direct/indirect/both), game pillars, any reference games the user mentioned, the game concept summary - Ask: "Shape the Player Fantasy for this system. What emotion or power fantasy should it serve? What player moment should we anchor to? What tone and language fits the game's established feeling? Be specific — give me 2-3 candidate framings." - Collect the creative-director's framings and present them to the user alongside the draft. **Do NOT draft Section B without first consulting `creative-director`.** The framing answer tells us *what kind* of fantasy it is; the creative-director shapes *how it's described* — tone, language, the specific player moment to anchor to. --- ### Section C: Detailed Design (Core Rules, States, Interactions) **Goal**: Unambiguous specification a programmer could implement without questions. This is usually the largest section. Break it into sub-sections: 1. **Core Rules**: The fundamental mechanics. Use numbered rules for sequential processes, bullets for properties. 2. **States and Transitions**: If the system has states, map every state and every valid transition. Use a table. 3. **Interactions with Other Systems**: For each dependency (upstream and downstream), specify what data flows in, what flows out, and who owns the interface. **Questions to ask**: - Walk me through a typical use of this system, step by step - What are the decision points the player faces? - What can the player NOT do? (Constraints are as important as capabilities) **Review mode check** (apply before spawning): - `solo` → skip this agent spawn. Draft the section without the specialist. Add a note: "Specialist agents not consulted — Solo mode. Review manually before production." - `lean` → skip unless t