Integrating device motion (gyroscope/accelerometer) with Metal shaders on iOS, and the MTKView fallback for when SwiftUI shaders are insufficient. Use this skill when the user wants to add tilt-reactive effects (parallax, specular highlights, holographic shimmer) driven by CMMotionManager, needs to wrap MTKView in SwiftUI via UIViewRepresentable, wants to render a shader result to an offscreen MTLTexture (bake/cache), or needs to optimize Metal shader performance and battery usage. Also trigger for questions about CMDeviceMotion attitude, render-to-texture patterns, Low Power Mode gating, or when to choose MTKView over SwiftUI shaders.
Metal Shading Language (MSL) techniques for 2D visual effects on iOS. Use this skill whenever writing or debugging MSL shader code for UI effects, procedural noise (Perlin, Simplex, Worley, fBm), signed distance fields (SDF shapes, antialiasing, boolean ops), hash functions for deterministic randomness, GLSL-to-MSL porting, or half vs float precision decisions. Also trigger when the user asks about fwidth, smoothstep for antialiasing, SDF text rendering, MSDF atlases, or procedural texture generation in Metal. This covers the non-obvious MSL knowledge that trips up engineers who know Swift but not GPU shading.
How to write and integrate Metal shaders into SwiftUI views using the iOS 17+ [[stitchable]] shader API. Use this skill whenever the user wants to add a Metal shader to a SwiftUI view, use .colorEffect / .distortionEffect / .layerEffect, pass arguments to a shader via ShaderLibrary, animate a shader with TimelineView, warm up shader compilation with Shader.compile(as:), or debug silent shader failures. Also use when the user asks about SwiftUI::Layer, stitchable attribute, Shader.Argument types, or maxSampleOffset. Trigger even for seemingly simple shader tasks — the API has many silent-failure pitfalls that this skill documents.
Implement, review, or improve WidgetKit widgets and controls. Use when building Home Screen, Lock Screen, StandBy, or CarPlay widgets with timeline providers; configurable widgets with AppIntentTimelineProvider; interactive widgets or Control Center controls with Button/Toggle wiring; WidgetKit push reloads, refresh budgets, deep links, Smart Stack relevance, Liquid Glass/accented rendering, widget extension setup, WidgetBundle, App Groups, and entitlements.