Expand a prototype GDD into a vertical slice GDD, adding polish, content scope, and quality bar definitions. Use this when prototype validates core mechanics and you're ready to build a polished representative slice.
This skill takes a validated prototype GDD and expands it into a comprehensive vertical slice GDD, defining the polished, representative experience that demonstrates final game quality.
Invoke this skill when the user:
Vertical slices prove the vision:
| Aspect | Prototype GDD | Vertical Slice GDD |
|---|---|---|
| Goal | Test core questions | Prove final quality |
| Scope | Minimum viable features | Polished representative slice |
| Quality | Functional, not polished | Final game quality |
| Content | Placeholder (3 enemies) | Polished subset (5 enemies, all final art) |
| Polish | No juice, basic feedback | Full juice, VFX, audio, animations |
| Duration | Weekend to week | 2-4 weeks |
| Success | "Does mechanic work?" | "Would I buy this game?" |
# [GAME TITLE] - Vertical Slice GDD
**Version:** [X.Y.Z]
**Based On:** Prototype GDD v[X.Y.Z]
**Prototype Validation Results:** [Summary of prototype success]
**Vertical Slice Goal:** [What this slice proves]
**Timeline:** [Weeks]
**Team Size:** [Number]
**Target Completion:** [Date]
---
## EXECUTIVE SUMMARY
### Prototype Validation Summary
**What We Tested:**
[List of critical questions from prototype GDD]
**Results:**
- Q1: [Question] → ✅ PASSED / ⚠️ NEEDS ITERATION / ❌ FAILED
- Q2: [Question] → [Result with evidence]
- Q3: [Question] → [Result]
**Key Learnings:**
- [Insight 1 from playtesting]
- [Insight 2]
- [Changes needed based on prototype feedback]
### Vertical Slice Vision
**What We're Proving:**
[1-2 paragraphs: What does this vertical slice demonstrate? What question does it answer?]
**Slice Scope:**
- **Duration:** [X minutes/hours of polished gameplay]
- **Content:** [Specific content included]
- **Quality Bar:** [Visual/audio quality target - comparable game reference]
---
## 1. WHAT'S IN THE VERTICAL SLICE
### Core Features (From Prototype)
[List features proven in prototype, now getting polished]
#### [Feature 1]: [Name]
**Prototype Status:** ✅ Validated
**Vertical Slice Enhancements:**
- [Polish item 1 - e.g., "Add VFX for all weapon fires"]
- [Polish item 2 - e.g., "Implement screen shake on damage"]
- [Polish item 3 - e.g., "Add audio SFX for all actions"]
- [Iteration item - e.g., "Refine targeting algorithm based on playtest feedback"]
**Quality Bar:**
[Description of final quality - e.g., "Weapon firing should feel impactful with muzzle flash VFX, screen shake, and punchy SFX"]
#### [Feature 2]: [Name]
[Same format]
---
### New Features (Additions to Prototype)
[Features not in prototype but needed for vertical slice]
#### [New Feature 1]: [Name]
**Why Adding:** [Justification - e.g., "Playtesters wanted more build variety"]
**Scope:** [Detailed description]
**Implementation Priority:** High / Medium / Low
**Dependencies:** [What must exist first]
**Acceptance Criteria:**
- [ ] [Criterion 1]
- [ ] [Criterion 2]
---
### Content Scope
**Total Content Volume:**
| Content Type | Prototype | Vertical Slice | Notes |
|--------------|-----------|----------------|-------|
| Enemy Types | 3 | 5 | Add Artillery and Elite |
| Weapon Types | 3 | 5 | Add Missiles and Flamethrower |
| Player Abilities | 0 | 0 | Not in slice scope |
| Arenas/Maps | 1 (basic) | 1 (polished) | Final art, not placeholder |
| Boss Fights | 0 | 1 | 15-min final boss |
| UI Screens | 3 | 6 | Add options, credits, how-to-play |
**Asset Production:**
- All placeholder art replaced with final quality
- All systems have audio SFX
- Background music (1 main theme, 1 boss theme)
- UI polished with animations and transitions
---
## 2. QUALITY BAR
### Visual Quality
**Art Style:** [Description - e.g., "Pixel art, 32x32 sprites, limited color palette"]
**Reference Quality:** [Comparable games - e.g., "Vampire Survivors polish level"]
**Specific Requirements:**
- **Player/Character:** [Animation requirements, visual polish]
- **Enemies/NPCs:** [Number of types, animation states, visual effects]
- **Interactions:** [What needs visual feedback - attacks, abilities, etc.]
- **UI:** [Polish level, animations, consistency]
- **VFX:** [Particle effects needed for key moments]
---
### Audio Quality
**Music:**
- [Track 1]: [Style, purpose - e.g., main theme, boss theme, etc.]
- [Track 2]: [Style, purpose]
**SFX:**
- [Category 1 sounds]: [Description - e.g., player actions, attacks]
- [Category 2 sounds]: [Description - e.g., enemy/NPC sounds]
- [Category 3 sounds]: [Description - e.g., UI sounds]
- Ambient: [Background ambience if applicable]
**Reference Quality:** [Comparable games or quality level]
---
### Game Feel (Juice)
**Required Polish:**
**Player Actions:**
- **[Core Action 1]:** [Polish requirements - particles, shake, sound, animation]
- **[Core Action 2]:** [Polish requirements]
- **[Important Moment 1]:** [Polish requirements]
- **[Important Moment 2]:** [Polish requirements]
**Interaction Feel:**
- **[Primary Interaction]:** [Visual/audio/haptic feedback]
- **[Impact/Hit Feedback]:** [Effects on successful action]
- **[Failure State]:** [How failure is communicated]
**UI Polish:**
- **Menu Transitions:** [Animation style and timing]
- **Button Interactions:** [Hover, click, feedback]
- **Progress Indicators:** [How bars/meters animate]
---
## 3. TECHNICAL REQUIREMENTS
### Performance Targets
**Vertical Slice Must Meet:**
- **FPS:** Solid 60 FPS with 100 enemies + 50 projectiles on screen
- **Load Time:** <2 seconds from menu to game
- **Memory:** <500 MB RAM usage
- **Build Size:** <100 MB (optimized assets)
**Optimizations Required:**
- Object pooling for bullets and enemies
- Off-screen culling for particles
- Cached targeting queries (not per-frame for all weapons)
---
### Code Quality
**Refactoring from Prototype:**
- [ ] All hardcoded values extracted to data files (.tres resources)
- [ ] Code quality issues from prototype refactored
- [ ] Scene optimization applied
- [ ] Architecture patterns established (signals, managers)
**Code Standards:**
- All scripts have type annotations
- No deprecated Godot 3.x syntax
- Signal connections documented
- Critical systems have comments
---
## 4. SCOPE BOUNDARIES
### What's IN the Vertical Slice
✅ **Gameplay:**
- Complete 15-minute run (tutorial difficulty)
- 5 weapon types with targeting rules
- 5 enemy types with distinct behaviors
- Level-up system with meaningful choices
- Final boss encounter at 15 minutes
✅ **Polish:**
- Final art for all assets
- Complete audio (music + SFX)
- Full juice (VFX, screen shake, animations)
- Polished UI with transitions
✅ **Screens:**
- Main menu (start, options, quit)
- Loadout screen (weapon rule setup)
- Game (HUD, pause menu)
- Level-up menu (upgrade choices)
- Death screen (stats, retry)
- Victory screen (if beat boss)
---
### What's OUT of Vertical Slice
❌ **Not Required:**
- Multiple difficulty modes (just balanced default)
- Meta-progression / unlocks (all content available)
- Multiple arenas (just 1 polished map)
- Endless mode beyond 15 minutes
- Leaderboards / online features
- Localization (English only)
- Advanced weapon rules (keep prototype's 2 rules: target + condition)
- Tutorial system (assume informed players)
- Cutscenes / story content
**Rationale:** Vertical slice proves core loop quality, not full game scope.
---
## 5. DEVELOPMENT PHASES
### Phase 1: [Phase Name] ([Timeline])
**Goal:** [What this phase accomplishes]
**Tasks:**
- [Task 1]
- [Task 2]
- [Task 3]
**Deliverable:** [Concrete output from this phase]
---
### Phase 2: [Phase Name] ([Timeline])
**Goal:** [What this phase accomplishes]
**Tasks:**
- [Task 1]
- [Task 2]
- [Task 3]
**Deliverable:** [Concrete output from this phase]
---
### Phase 3: [Phase Name] ([Timeline])
**Goal:** [What this phase accomplishes]
**Tasks:**
- [Task 1]
- [Task 2]
- [Task 3]
**Deliverable:** [Concrete output from this phase]
---
### Phase 4: [Phase Name] ([Timeline])
**Goal:** [What this phase accomplishes]
**Tasks:**
- [Task 1]
- [Task 2]
- [Task 3]
**Deliverable:** [Concrete output from this phase]
---
## 6. SUCCESS CRITERIA
### Validation Questions
**The vertical slice succeeds if it answers YES to:**
1. **Quality Question:** "Does this look/sound/feel like a finished game?"
- External viewers assume it's close to release
- No placeholder art or missing audio
- Polish comparable to commercial indie games
2. **Engagement Question:** "Would I pay money for more of this?"
- Playtesters want to continue beyond 15 minutes
- "When's the full game coming?" reactions
- Positive sentiment without major complaints
3. **Repeatability Question:** "Do I want to replay with different strategies?"
- Players retry with different weapon setups
- Discussion of optimal builds
- "One more run" engagement
4. **Vision Question:** "Does this prove the full game concept?"
- Stakeholders/publishers understand the full game vision
- Scaling this slice to full game feels achievable
- Core loop is proven and compelling
---
### Quantitative Targets
**Playtesting Metrics:**
- 80%+ complete full 15-minute run (not too hard)
- 60%+ retry after first run (engagement)
- Average 3+ runs per playtest session (replayability)
- 8/10+ satisfaction rating (quality)
**Technical Metrics:**
- 60 FPS maintained 95%+ of time
- Zero critical bugs
- <2 second load times
---
## 7. RISK ASSESSMENT
### Risks from Prototype
**Known Issues from Prototype:**
1. [Issue 1 from prototype playtest]
- Mitigation: [How vertical slice addresses this]
2. [Issue 2]
- Mitigation: [Solution]
### New Risks for Vertical Slice
**Risk: Art production takes longer than expected**
- Impact: HIGH (delays entire slice)
- Mitigation: Parallel art production, start Week 1
- Fallback: Reduce enemy types from 5 to 4
**Risk: Audio integration is complex**
- Impact: MEDIUM (affects polish)
- Mitigation: Use Godot AudioStreamPlayer, simple setup
- Fallback: Reduce SFX count, prioritize critical sounds
**Risk: Performance doesn't meet 60 FPS target**
- Impact: HIGH (quality bar not met)
- Mitigation: Object pooling, profiling in Week 3
- Fallback: Reduce max enemy count, optimize VFX
---
## 8. POST-SLICE DECISION TREE
### If Slice Succeeds (Validation Positive)
**Next Steps:**
1. Create Production GDD for full game
2. Plan content pipeline and team scaling
3. Estimate full production timeline
4. Seek funding/publishing if needed
**Full Game Scope:**
- [Expand from slice - e.g., "10 weapons, 15 enemy types, 5 arenas, 60-min endgame"]
---
### If Slice Needs Iteration
**Identify Issues:**
- [ ] Polish not at quality bar → More art/audio time
- [ ] Balance feels off → Tuning pass
- [ ] Core loop still unclear → Return to prototype, test variations
**Iteration Plan:**
- [Address specific issues]
- Retest in 1-2 weeks
---
### If Slice Fails Validation
**Pivot Options:**
- Return to prototype, test different mechanics
- Reduce scope (simpler game, faster to market)
- Cancel project (better to fail fast)
---
## 9. DELIVERABLES
### Final Vertical Slice Build
**Contents:**
- Standalone executable (Windows/Mac/Linux)
- 15-minute polished gameplay experience
- All final art and audio
- Presentation-ready (show to publishers/investors)
**Documentation:**
- This Vertical Slice GDD
- Playtest results summary
- Known issues log (minor bugs acceptable)
- Full game vision document (if proceeding to production)
---
## 10. BUDGET & RESOURCES
### Time Budget
**Total:** 4 weeks (160 hours for solo dev)
**Breakdown:**
- Programming: 60 hours (refactor, features, optimization)
- Art: 50 hours (sprites, animations, VFX)
- Audio: 20 hours (music, SFX, integration)
- Design/Balance: 20 hours (tuning, playtesting)
- Polish: 10 hours (final touches, bug fixes)
### Asset Needs
**Art:**
- Player sprite + animations (4 hours)
- 5 enemy sprites + animations (15 hours)
- 5 weapon projectile sprites (5 hours)
- UI art (10 hours)
- VFX sprites (8 hours)
- Background/arena (8 hours)
**Audio:**
- Music (2 tracks): 8 hours or $200 for composer
- SFX (30 sounds): 8 hours or $150 for SFX pack
- Integration: 4 hours
---
## APPENDICES
### Appendix A: Prototype Playtest Results
[Detailed findings from prototype validation]
### Appendix B: Reference Games Quality Comparison
[Screenshots/analysis of comparable games' polish level]
### Appendix C: Asset List
[Complete list of all art/audio assets needed]
---
**END OF VERTICAL SLICE GDD**
This document defines the polished representative slice that proves the game is worth building fully.
Ask user for prototype GDD location:
docs/[game]-prototype-gdd.mdRead prototype GDD:
Ask about prototype results:
Ask user:
Based on the prototype, let's define the vertical slice scope:
**1. What's the target experience duration?**
- Prototype was [X duration], vertical slice should be [Y duration]?
- What feels like a complete experience for your game type?
**2. What content expands from prototype?**
- What content types exist in prototype? (enemies, levels, abilities, etc.)
- How much content should vertical slice have?
- Any new features to add beyond prototype?
**3. What's the quality bar?**
- Visual reference: Which game's polish level?
- Audio: Full music + SFX, or just SFX?
- Juice: Full VFX, screen shake, particles?
**4. What's the timeline?**
- Typical: 2-4 weeks for vertical slice
- Your availability: [Hours per week]?
**5. What's the vertical slice proving?**
- What question must this slice answer?
- Who needs to be convinced? (yourself, team, publisher, players)
Wait for responses.
Ask about polish requirements:
Let's define the quality bar:
**Visual Polish:**
- Replace all placeholder art? (Yes/No)
- Art style: [Pixel/Vector/3D/Minimal]?
- Reference quality: [Game name]?
**Audio:**
- Music tracks needed: [Main theme, boss theme, menu]?
- SFX coverage: [All actions, or just critical ones]?
**Game Feel (Juice):**
- Screen shake: [Always, sometimes, never]?
- Particle effects: [Minimal, moderate, heavy]?
- Damage numbers: [Yes/No]?
- UI animations: [Yes/No]?
**Performance:**
- FPS target: [30/60]?
- Max enemies on screen: [Number]?
Break timeline into phases:
Calculate total hours:
Suggest phase breakdown:
Assign tasks to phases based on dependencies
Create comprehensive document with:
Save to: docs/[game]-vertical-slice-gdd.md
User: "Expand [game] prototype GDD to vertical slice"
Skill:
I'll expand the [game] prototype GDD to a vertical slice GDD.
Reading prototype GDD... Found:
- [X] critical questions tested
- [Prototype structure/scope]
- Prototype validation: [SUCCESS/NEEDS ITERATION]
Now let's define the vertical slice:
**1. Timeline:** How long for vertical slice?
Prototype was [X duration]. Vertical slice typically 2-4 weeks.
Recommended: [X weeks] for [team size]
**2. Quality Bar:** What's the reference quality?
Prototype: [Current state]
Vertical Slice: Which game's polish level should we target?
**3. Content Scope:** Expand or keep same?
Prototype: [Content summary]
Vertical Slice: Same content but fully polished? Or add more?
**4. New Features:** Any additions based on prototype feedback?
Prototype feedback: [Key findings]
What should be addressed in vertical slice vs saved for production?
prototype-gdd-generator - Reads prototype GDD as inputvertical-slice-roadmap-planner - Takes vertical slice GDD, creates feature roadmapproduction-gdd-generator - Vertical slice proves concepts for full production GDDfeature-spec-generator - Each new feature in slice gets detailed specbalance-tuner - Balance pass is part of vertical slice developmentjuice-guide - Polish requirements defined in quality bar sectionBefore finalizing vertical slice GDD:
User: "Expand prototype GDD to vertical slice" User: "Create vertical slice GDD from prototype" User: "Plan vertical slice for Mech Survivors" User: "Prototype validated, what's next?" → Skill suggests vertical slice GDD
docs/[game]-vertical-slice-gdd.mdvertical-slice-roadmap-planner next to create feature roadmapPrototype validated: "Program weapon rules → watch execution → iterate" works Vertical Slice adds: VFX, audio, 5 polished weapons, boss fight, full juice Timeline: 3-4 weeks Quality bar: Vampire Survivors polish level
Prototype validated: Core movement + 3 puzzle mechanics work well Vertical Slice adds: 10 polished levels, final art, music, level transitions Timeline: 2-3 weeks Quality bar: Celeste polish level
Prototype validated: Grid combat + unit abilities feel tactical Vertical Slice adds: 5 unit types, 3 polished maps, AI, full UI Timeline: 4 weeks Quality bar: Into the Breach polish level
This skill bridges the gap between "it works" (prototype) and "it's polished" (vertical slice), setting the quality bar for full production.