animation-patterns

1# Animation Patterns
2 
3Correct API shapes and patterns for SwiftUI animations. Prevents the most common mistakes: mixed spring parameter generations, wrong PhaseAnimator/KeyframeAnimator closure signatures, and using matchedGeometryEffect where matchedTransitionSource is needed.
4 
5## When This Skill Activates
6 
7Use this skill when the user:
8- Asks to add, fix, or review **animation** code
9- Mentions **spring**, **bounce**, or **snappy** animations
10- Wants **view transitions** (insertion/removal, hero, zoom)
11- Asks about **PhaseAnimator** or **KeyframeAnimator**
12- Wants **SF Symbol effects** (bounce, pulse, wiggle, breathe)
13- Mentions **matchedGeometryEffect** or **matchedTransitionSource**
14- Asks about **reduce motion** / animation accessibility
15- Wants to sequence or chain animations
16- Mentions **withAnimation**, **animation completions**, or **Transaction**
17- Wants **scroll-driven effects** (parallax, carousels, `scrollTransition`, `visualEffect`)
18- Mentions **MeshGradient**, **TextRenderer**, or **Metal shader effects** (`colorEffect`, `distortionEffect`, `layerEffect`)
19 
20## Decision Tree
21 
22Choose the right reference file based on what the user needs:
23 
24```
25What are you animating?
26│
27├─ A state change (opacity, position, color)
28│  └─ → core-animations.md
29│     ├─ withAnimation { } — explicit animation
30│     ├─ .animation(_:value:) — implicit animation
31│     └─ Spring configuration — .spring, .bouncy, .snappy, .smooth
32│
33├─ A multi-step / sequenced animation
34…