axiom-games - SKILL.md Agent Skill

name: axiom-games description: Use when building ANY 2D or 3D game with SpriteKit, SceneKit, or RealityKit, or adding touch controls or game controller support. Covers scene graphs, ECS, physics, actions, game loops, rendering, TouchController, GCController. license: MIT

Games

You MUST use this skill for ANY game development, SpriteKit, SceneKit, RealityKit, touch controls, game controller, or interactive simulation work.

Quick Reference

Symptom / Task	Reference
Building a SpriteKit game	See `skills/spritekit.md`
Adding touch controls to a game (TouchController)	See `skills/game-input.md`
Game controller input (GCController, polling vs handlers)	See `skills/game-input.md`
Controller Home button settings, spatial accessories `OS27`	See `skills/game-input.md`
SpriteKit API lookup	See `skills/spritekit-ref.md`
Physics contacts not firing	See `skills/spritekit-diag.md`
Frame rate drops (SpriteKit)	See `skills/spritekit-diag.md`
Touches not registering	See `skills/spritekit-diag.md`
Memory spikes in gameplay	See `skills/spritekit-diag.md`
Coordinate confusion	See `skills/spritekit-diag.md`
Scene transition crashes	See `skills/spritekit-diag.md`
Objects tunneling through walls	See `skills/spritekit-diag.md`
SpriteKit node/action reference	See `skills/spritekit-ref.md`
SceneKit maintenance/migration	See axiom-graphics (skills/scenekit.md)
SceneKit API / migration mapping	See axiom-graphics (skills/scenekit-ref.md)
RealityKit (3D, ECS, AR)	See axiom-graphics (skills/realitykit.md)
RealityKit API reference	See axiom-graphics (skills/realitykit-ref.md)
RealityKit diagnostics	See axiom-graphics (skills/realitykit-diag.md)
RealityKit 27 game features (navmesh, LOD, splats)	See axiom-graphics (skills/realitykit-ref.md Part 10)
Long-session game performance tracing (metalperftrace)	See axiom-graphics (skills/display-performance.md Part 12)
Porting a Mac/Windows game to Metal	See axiom-graphics (skills/metal-migration.md)
In-game content, asset packs, IAP	See axiom-integration (skills/background-assets.md, skills/in-app-purchases.md)

External Routes

These topics are part of the broader games/3D domain but live in separate skill suites:

SceneKit (3D — soft-deprecated iOS 26):

Maintenance and migration planning → See axiom-graphics (skills/scenekit.md)
API reference and migration mapping → See axiom-graphics (skills/scenekit-ref.md)

RealityKit (3D — modern):

ECS architecture, AR, SwiftUI integration → See axiom-graphics (skills/realitykit.md)
API reference → See axiom-graphics (skills/realitykit-ref.md)
Troubleshooting → See axiom-graphics (skills/realitykit-diag.md)
27-cycle game-engine layer: navigation mesh + pathfinding, behavior trees, animation graphs, LOD, Gaussian splats → See axiom-graphics (skills/realitykit-ref.md Part 10)

Game performance and porting:

Long-session game traces, metalperftrace CLI, Game Performance Overview template → See axiom-graphics (skills/display-performance.md Part 12)
Metal migration, shader conversion → See axiom-graphics (skills/metal-migration.md)

In-game content and monetization:

Apple-Hosted Background Assets, asset packs, Steam depot conversion → See axiom-integration (skills/background-assets.md)
In-app purchase, StoreKit views → See axiom-integration (skills/in-app-purchases.md)

Decision Tree

digraph games {
    start [label="Game development" shape=ellipse];
    what [label="Which framework?" shape=diamond];
    sprite_what [label="SpriteKit need?" shape=diamond];

    start -> what;
    what -> sprite_what [label="SpriteKit (2D)"];
    what -> "skills/game-input.md" [label="touch controls / game controllers"];
    what -> "axiom-graphics/scenekit" [label="SceneKit (3D legacy)"];
    what -> "axiom-graphics/realitykit" [label="RealityKit (3D modern)"];
    what -> "axiom-graphics/metal-migration" [label="porting (Metal)"];

    sprite_what -> "skills/spritekit.md" [label="architecture/patterns"];
    sprite_what -> "skills/spritekit-ref.md" [label="API lookup"];
    sprite_what -> "skills/spritekit-diag.md" [label="broken/slow"];
}

Building/designing a 2D SpriteKit game? → skills/spritekit.md
How to use a specific SpriteKit API? → skills/spritekit-ref.md
SpriteKit broken or performing badly? → skills/spritekit-diag.md
Adding touch controls, or handling game controller input? → skills/game-input.md
Maintaining existing SceneKit code? → See axiom-graphics (skills/scenekit.md)
SceneKit API reference or migration mapping? → See axiom-graphics (skills/scenekit-ref.md)
Building new 3D game or experience? → See axiom-graphics (skills/realitykit.md)
How to use a specific RealityKit API? → See axiom-graphics (skills/realitykit-ref.md)
RealityKit entity not visible, gestures broken, performance? → See axiom-graphics (skills/realitykit-diag.md)
Migrating SceneKit to RealityKit? → See axiom-graphics (skills/scenekit.md) (migration tree) + See axiom-graphics (skills/scenekit-ref.md) (mapping table)
Building AR game? → See axiom-graphics (skills/realitykit.md)
Porting a Mac/Windows game to Apple platforms? → See axiom-graphics (skills/metal-migration.md)
Unlocking in-game content (asset packs, IAP)? → See axiom-integration (skills/background-assets.md, skills/in-app-purchases.md)
Want automated SpriteKit code scan? → spritekit-auditor agent

Automated Scanning

SpriteKit audit → Launch spritekit-auditor agent or /axiom:audit spritekit

Detects anti-patterns AND architectural gaps:

Physics bitmask issues (default 0xFFFFFFFF, missing contactTestBitMask, magic numbers)
Draw call waste (SKShapeNode in gameplay, missing texture atlases)
Node accumulation and runaway spawn-in-update() without cleanup
Action memory leaks (strong self, .repeatForever without withKey:)
Coordinate confusion (touch.location(in: self.view) instead of in: self)
Silent input dead zones (custom touchesBegan without isUserInteractionEnabled)
Missing object pooling for hot spawns
Missing/ungated debug overlays
Leaked scenes (transition without removeAllActions() and child cleanup)
Missing time-step clamping → spiral-of-death teleports bodies through walls
HUD attached to scene root instead of camera (drifts with scrolling)
Fast bodies without usesPreciseCollisionDetection (tunneling)

Scores: PERFORMANT / DEGRADED / UNPLAYABLE

Critical Patterns

SpriteKit (skills/spritekit.md):

PhysicsCategory struct with explicit bitmasks (default 0xFFFFFFFF causes phantom collisions)
Camera node pattern for viewport + HUD separation
SKShapeNode pre-render-to-texture conversion
[weak self] in all SKAction.run closures
Delta time with spiral-of-death clamping

SpriteKit diagnostics (skills/spritekit-diag.md):

5-step bitmask checklist (2 min vs 30-120 min guessing)
Debug overlays as mandatory first diagnostic step
Tunneling prevention flowchart
Memory growth diagnosis via showsNodeCount trending

Game input (skills/game-input.md):

One GCController pipeline — touch controls surface as a GCController, existing logic unchanged
TCTouchController.isSupported gate + connect/render/touch-routing setup
Half-screen collider shapes for movement and camera (never small circles)
Safe-area-adjusted anchor offsets for fullscreen games
Controller Home button settings + visionOS spatial accessories OS27

Anti-Rationalization

Thought	Reality
"SpriteKit is simple, I don't need a skill"	Physics bitmasks default to 0xFFFFFFFF and cause phantom collisions. The bitmask checklist catches this in 2 min.
"I'll just use SKShapeNode, it's quick"	Each SKShapeNode is a separate draw call. 50 of them = 50 draw calls. spritekit.md has the pre-render-to-texture pattern.
"I can figure out the coordinate system"	SpriteKit uses bottom-left origin (opposite of UIKit). Anchor points add another layer. spritekit-diag.md Symptom 6 resolves in 5 min.
"Physics is straightforward"	Three different bitmask properties, modification rules inside callbacks, and tunneling edge cases. spritekit.md Section 3 covers all gotchas.
"The performance is fine on my device"	Performance varies dramatically across devices. spritekit.md Section 6 has the debug overlay checklist.
"SceneKit is fine for our new project"	SceneKit is soft-deprecated iOS 26. No new features, only security patches. axiom-graphics (skills/scenekit.md) has the migration decision tree.
"ECS is overkill for a simple 3D app"	You're already using ECS — Entity + ModelComponent. axiom-graphics (skills/realitykit.md) shows how to scale from simple to complex.
"I don't need collision shapes for taps"	RealityKit gestures require CollisionComponent. axiom-graphics (skills/realitykit-diag.md) diagnoses this in 2 min vs 30 min guessing.
"I'll overlay UIButtons for touch controls"	TouchController renders in your Metal pass and surfaces as a GCController — existing controller logic just works. UIButton overlays mean a second input path and per-frame UIKit cost. game-input.md Section 2.
"Touch controls = put every controller button on screen"	A 1:1 mapping clutters the play area and demands 3+ fingers. game-input.md Section 5 has the redesign patterns (context icons, hide unused, collapse combos).

Example Invocations

User: "I'm building a SpriteKit game" → See skills/spritekit.md

User: "My physics contacts aren't firing" → See skills/spritekit-diag.md

User: "How do I create a physics body from a texture?" → See skills/spritekit-ref.md

User: "Frame rate is dropping in my game" → See skills/spritekit-diag.md

User: "What action types are available?" → See skills/spritekit-ref.md

User: "Objects pass through walls" → See skills/spritekit-diag.md

User: "I'm porting my controller game to iPhone and need touch controls" → See skills/game-input.md

User: "How do I handle game controller input?" → See skills/game-input.md

User: "How do I read spatial accessory input on visionOS?" → See skills/game-input.md

User: "I need to build a 3D game" → Invoke: See axiom-graphics (skills/realitykit.md)

User: "I'm migrating from SceneKit to RealityKit" → Invoke: See axiom-graphics (skills/scenekit.md) + See axiom-graphics (skills/scenekit-ref.md)

User: "Can you scan my SpriteKit code for common issues?" → Launch spritekit-auditor agent