Unity Script Design Review

Use this skill before creating gameplay scripts, or after scripts are generated and need a design pass.

Review Checklist

• Responsibility: does the script have one clear job?
• Role: should it really be a MonoBehaviour, ScriptableObject, or plain C# class?
• Coupling: are dependencies explicit instead of hidden globals or deep scene lookups?
• Communication: should this be a direct reference, interface call, or event?
• Performance: is there unnecessary Update, repeated Find, avoidable allocation, or reflection in hot paths?
• Lifecycle: are subscriptions, timers, and async work cleaned up clearly?
• Inspector UX: are serialized fields private, grouped, and explained?
• Testability: can the core logic move into a plain C# class?
• Naming: do class and field names explain intent without cryptic abbreviations?

Data Lifecycle Boundary

The Review Checklist above asks "where does this class live". Ask the same question for every field. Every piece of state has one of three lifecycles, and putting a field on the wrong one is the most common cause of "why did this break when the designer tweaked a value" and "why are my unit tests flaky".

Lifecycle	When the value is decided	Where it belongs	Typical idiom
Authoring-time	By a designer in the Editor, before Play	ScriptableObject asset, or [SerializeField] private on a prefab	Immutable at runtime; read via _config.Speed
Composition-time	Once per scene/instance, at Awake/Start	private field, assigned from GetComponent / GetComponentInChildren / ctor arg	Cached reference, no per-frame lookup
Runtime-mutable	Every frame or on gameplay events	private backing field + public read-only property + event	Exposed via public float Health { get; private set; } + OnHealthChanged

Typical assignments

• Weapon damage / fire rate / clip size → Authoring-time (ScriptableObject so balance can be hot-swapped).
• Enemy AI's current target Transform → Composition-time if set once at spawn, Runtime-mutable if re-targeted each frame.
• Player current HP → Runtime-mutable with event. Never public float hp;.
• Reference to Rigidbody/Animator on the same GameObject → Composition-time, cached in Awake.
• Level music track → Authoring-time via ScriptableObject level descriptor.
• "Is in combat" flag → Runtime-mutable, but usually derived from other state — review whether it should be a field at all.

Why the separation matters

Mixing the three lifecycles is what turns a clean class into a god object. A MonoBehaviour whose public float speed is edited by both the Inspector and a power-up script has two owners and no invariant; a bug in either path corrupts the other. The ECS baking pipeline makes this distinction a hard architectural boundary (Authoring → Baker → System), and the discipline transfers directly: if you would not mix an Authoring component with runtime write-back in ECS, do not mix them in a MonoBehaviour either. Source: EntitiesSamples/Docs/baking.md:5-16.

Guardrails

Mode: Both (Semi-Auto + Full-Auto) — advisory only, no REST skills

• Prefer descriptive names over local shorthand.
• Do not “optimize” readability away for imagined productivity gains.
• Do not recommend complex patterns if a smaller refactor fixes the real problem.

Output Format

• Keep: what is already good
• Simplify: what should stay straightforward
• Refactor: the highest-value structural change
• Performance notes: only real hotspots, not theoretical micro-optimizations
• Maintainability notes: naming, ownership, coupling, editor usability