A vague prompt makes a vague prototype. That is the pattern I see most often with AI game builders. The tool gives you something playable enough to look impressive, but not precise enough to answer the question you actually had.
Before you ask any tool to build the first version, write a prototype contract. Not a design document. Not a roadmap. A short agreement with yourself about what this draft must prove, what it must ignore, and what result will make you keep working.
This is a practical workflow article for solo builders and small teams using AI-assisted game development. It focuses on prototype framing, not on one vendor or release news.
Godot
A good fit when a proven 2D prototype needs custom systems, clean scene structure, and direct scripting control.
Unity
A fit for teams that already know the toolchain or need a larger production path after the prototype earns it.
Construct
A browser-focused editor that can be useful when you want visual logic and fast playable iteration.
GDevelop
A visual game builder that works well for simple rule tests and readable event logic.
The Contract Has Four Lines
Keep it plain. One sentence for the player action. One sentence for the pressure. One sentence for the constraint. One sentence for the pass or fail condition. If you cannot write those four lines, you are not ready to prompt the prototype yet.
The prompt should implement the contract. It should not invent the contract.
Weak Prompt vs Prototype Contract
| Part | Weak version | Contract version |
|---|---|---|
| Player action | Make a fun arcade game | The player dashes through one-tile gaps to collect fuel |
| Pressure | Add enemies | The fuel meter drains faster after every missed dash |
| Constraint | Make it polished | Use one room, one enemy type, and no upgrade shop |
| Exit criteria | See if it feels good | Keep it only if three retries happen without explanation |
Constraints Make AI More Useful
AI tools are good at filling empty space. That is a problem during early prototyping. If you leave the request open, you get menus, lore, particles, extra enemies, and half a progression system before you know whether the main verb works.
A contract gives the tool less room to decorate. It tells the draft what not to solve yet. No shop. No story intro. No second biome. No permanent upgrades. The smaller the box, the easier it is to tell whether the core idea has pressure.
Lock the verb
You are still testing what the player does every five seconds.
Movement games, action loops, puzzle interactions, and arcade tests.Lock the pressure source
The prototype needs tension, but you do not know which threat creates it.
Timers, chasing enemies, shrinking arenas, limited ammo, and score decay.Lock the content budget
The tool keeps adding levels and features before the first room works.
Keeping the first playable readable and cheap to throw away.- The player action fits in one sentence.
- The pressure source changes player behavior.
- The draft has one room or one repeated situation.
- The prompt forbids at least three distractions.
- The pass or fail condition can be observed in a five-minute test.
- The next prompt changes the contract only after you play the draft.
If the prototype contract is fuzzy, the generated game will be fuzzy too. Tighten the test before you ask for the build.
FAQ
What is a prototype contract for an AI game?
It is a short test definition written before prompting: player action, pressure source, constraint, and pass or fail condition.
Is this the same as a game design document?
No. A design document explains the broader game. A prototype contract exists to make one playable draft testable.
Should I write the contract before choosing an engine?
Usually, yes. The contract tells you whether you need fast visual iteration, engine control, export targets, or just a disposable draft.