Writing Game Design Document (GDD) for Mobile Game
GDD — team working tool, not marketing document. Bad GDD: 40 pages of inspiring text about "captivating game world" without single number or diagram. Good GDD: artist understands style via moodboard and color table, developer — via state machine diagram and numeric parameters, QA — via acceptance criteria checklist for each feature.
GDD Structure for Mobile Game
Mobile game GDD differs from PC/console — it's more compact, focuses on touch interaction and mobile constraints, includes monetization section from page one (this isn't shameful, it's market reality).
Overview and Concept
One paragraph: genre, target audience, USP (unique selling point). References: 2–3 existing games with specific indication of what we borrow and what we do differently. Moodboard: 10–15 images of visual style.
Not "adventure game in fantasy world". But "match-3 with RPG progression in Puzzle & Dragons style, but with asynchronous PvP and no energy mechanic".
Core Mechanics
For each mechanic: name, 2–3 sentence description, user story ("as player, I want X so that Y"), state machine diagram, input events (tap, swipe, hold), parameters with default values and allowed ranges.
Example parameters for "throw" mechanic in physics puzzle:
throw_power_min: 200 [100-400]
throw_power_max: 1500 [800-2500]
gravity_scale: 1.2 [0.8-2.0]
bounce_factor: 0.6 [0.3-0.9]
max_trajectory_points: 20 [10-40]
These parameters — ScriptableObject in Unity. Game designer changes without programmer.
UI/UX Specification
Wireframes for each screen — not final design but element placement, tap target sizes (minimum 44×44pt per Apple HIG), information hierarchy. Navigation map: all screens + transitions.
For mobile separately: behavior on interrupt (call, notification), behavior on connection loss, orientation (portrait only, landscape only, both), Safe Area for notched iPhone.
Monetization
Concrete model with numbers: free-to-play + IAP, premium ($2.99 upfront), rewarded ads (goal: eCPM $8–15 for casual). Each IAP description: what we sell, pricing, where in UI we offer. Soft currency vs hard currency — sources (earning) and sinks (spending).
Energy mechanic if present: initial supply, regen time, maximum, ways to buy more. Specifically: 5 lives, regenerate 1 life/30 min, max 5, full regen 100 gems, 1 IAP life — 20 gems.
Technical Requirements
Target platforms: iOS 15+, Android 8.0+. Engine: Unity 2023 LTS / Godot 4.x / Cocos Creator 3.x. Target FPS: 60 on iPhone 12+, 30+ on Android mid-range (Snapdragon 665+). Build size: up to 100 MB for first download (App Store / Play Store recommendations for cellular). Asset streaming if needed.
From practice: hyper-casual game, 4-person team with no GDD. Artist drew character in realistic style, developer implemented mechanic oriented to landscape, marketer shot trailer with gameplay not yet made. After three weeks realized artist, developer, marketer working on different games. GDD written 2 days before dev start would have saved 2 weeks rework.
Detail Level
GDD — living document. Don't need describe every particle before development. Need describe:
- Core mechanics — completely, to numeric parameters
- First hour experience — in detail
- Content plan (levels, chapters, events) — structure without each level details
- Monetization — completely
Level design of specific levels — in separate Level Design Documents (LDD), when reached.
Formats and Tools
GDD in Notion / Confluence — convenient for team work, versioning, comments. Alternative — Google Docs with table of contents. Diagrams — Miro or draw.io (FigJam). Balance tables — Google Sheets (not in GDD, link from GDD).
Don't write GDD in Word without version control — after month no one knows which version is actual.
What's Involved
- Concept interviews (1–2 hours)
- Overview and concept document with references and moodboard
- Description of all core mechanics with diagrams and parameters
- UI/UX wireframes for key screens
- Application navigation map
- Monetization specification
- Technical requirements
- Content plan (levels, events, DLC)
Timeline
3–5 working days — GDD for hyper-casual or casual game. For midcore / hardcore project with complex systems — 7–14 days. Cost calculated individually.