Unity Architecture

Unity Architecture Advisor

Use this before generating lots of gameplay scripts or when the user asks for a cleaner architecture.

Workflow

• Identify scope: prototype, small game, or long-lived project.
• Define the core loop and the minimum runtime systems needed.
• Recommend the smallest architecture that fits the scope.
• Separate:
• scene/bootstrap layer
• gameplay/domain logic
• data/config assets
• view/presentation layer
• Call out what should stay simple now vs what is worth abstracting.

Output Format

When using this skill, structure the advice as:

• Project tier: prototype / small-game / long-lived
• Recommended modules: 3-7 modules with one-line responsibilities
• Scene/bootstrap plan: where composition and initialization happen
• Data ownership: what belongs in scene objects, ScriptableObjects, or pure C# classes
• Communication rules: direct refs, interfaces, events, or commands
• Performance risks: only the hot paths that matter
• Do now / skip now: avoid over-engineering

Default Guidance

• Prefer thin MonoBehaviour scripts as composition bridges.
• Put reusable gameplay rules in plain C# classes when possible.
• Use ScriptableObject for authored config and shared static data, not as a default dump for runtime state.
• Keep dependencies explicit. Avoid hidden global state unless the project size clearly justifies a small service layer.
• Favor simple module boundaries over framework-heavy architecture.

Explicit Execution Order and Entry Guards

Most "random" gameplay bugs trace back to two silent assumptions: that scripts run in a predictable order, and that Update runs only when its data is ready. Neither is true unless you make them so.

Make startup order explicit

Do not rely on Script Execution Order panels or accidental Awake ordering. Prefer these patterns in order of preference:

• One Bootstrap script as the single entry point. It owns the initialization sequence and calls sub.Init() on the managers it creates. Only this one script has [DefaultExecutionOrder(-10000)].
• Pull, don't push: a subscriber that needs data calls source.GetValue() on demand or subscribes to an event. A publisher that pushes into others during its own Awake creates hidden order dependencies.
• Reserve [DefaultExecutionOrder(n)] for load-bearing singletons only (Bootstrap, InputRouter, SceneController). If more than 3-4 scripts need it, the architecture is wrong, not the ordering.

The analogous ECS pattern — [UpdateBefore(typeof(BarSystem))] / [UpdateAfter] — works because the framework validates contradictions at sort time. In MonoBehaviour code the compiler won't catch them; be conservative. *Source: EntitiesSamples/Docs/systems.md:32 — "if the ordering attributes of a group's children create a contradiction, an exception is thrown".*

Make update preconditions explicit

Every Update / LateUpdate / FixedUpdate should open with guard clauses that early-return when the system is not ready. Prefer the cheapest check first:

void Update() {
    if (!_isInitialized) return;       // construction-time
    if (_dataSource == null) return;   // dependency-level
    if (_paused) return;               // gameplay-state
    // real work here
}

A missing guard is the difference between "doesn't run yet" (safe) and "runs with stale/null data and silently corrupts state" (debug nightmare). The ECS equivalent is state.RequireForUpdate<Config>() in OnCreate, which turns the precondition into a system-level invariant. *Source: Dots101/Entities101/Assets/HelloCube/3. Prefabs/SpawnSystem.cs:17-19 — the system does not update unless a Spawner entity exists.*

Guardrails

> Mode: Documentation only — no REST skills to gate; load freely under any operating mode (Approval / Auto / Bypass).

• Do not start from a giant reusable framework unless the project truly needs it.
• Do not add layers just to satisfy textbook SOLID wording.
• Prefer a small architecture that can grow, not an impressive one that slows iteration.

Load Related Advisory Modules When Needed

• Pattern choice: see ../patterns/SKILL.md
• Async / Update / UniTask decisions: see ../async/SKILL.md
• Inspector-facing field design: see ../inspector/SKILL.md
• Script quality review: see ../scriptdesign/SKILL.md