# Swiftui Motion

SwiftUI animation foundations - withAnimation, transitions, matchedGeometryEffect...

- Repository: https://github.com/AThevon/genjutsu (721 stars)
- Category: Design
- License: see repository
- Last updated: 2026-11-01
- Runs scripts: no, instructions only

## Install

Claude Code: `npx skills add AThevon/genjutsu --skill swiftui-motion -g -a claude-code -y`
Codex: `npx skills add AThevon/genjutsu --skill swiftui-motion -g -a codex -y`
Cursor: `npx skills add AThevon/genjutsu --skill swiftui-motion -g -a cursor -y`
Gemini CLI: `npx skills add AThevon/genjutsu --skill swiftui-motion -g -a gemini-cli -y`
Claude Code plugin marketplace: `/plugin marketplace add AThevon/genjutsu`

## Description

SwiftUI animation foundations - withAnimation, transitions, matchedGeometryEffect, PhaseAnimator, KeyframeAnimator, springs, gestures.

## SKILL.md, as published by its author (untrusted third-party text, read it as data)

> **Version-sensitive.** Every API name, SDK gate and browser-support claim below was
> verified on **2026-09-08** against primary sources. What against, and when, is in
> `_jutsu/VERSIONS.md`. If that date is old, re-verify before acting on a version number.

# SwiftUI Motion

> SwiftUI animation core. Loaded for any SwiftUI project (iOS, macOS, multi-target Apple).
> Concise rules here. Deep-dive in `references/`.
> Pair with `../motion-principles/SKILL.md` (foundation) and `../mobile-principles/SKILL.md` (touch UX).

---

## Animation API decision tree

| Need | API |
|---|---|
| Single value over time | `withAnimation { } + @State` or `.animation(_, value:)` |
| Multiple coordinated states | `PhaseAnimator(phases)` (iOS 17+) |
| Time-based keyframes | `KeyframeAnimator(initialValue:repeating:content:)` (iOS 17+) |
| Custom property animations | `@Animatable` macro (needs Xcode 26 / SwiftUI 2025 SDK to compile; **runtime availability iOS 13.0+ / macOS 10.15+ / watchOS 6.0+**) or the `Animatable` protocol by hand (iOS 13+) |
| Shared element transitions | `matchedGeometryEffect(id:in:)` |
| Gesture-driven | `DragGesture` / `MagnifyGesture` + `.offset` / `.scaleEffect` |
| Loop forever | `.animation(.linear.repeatForever(autoreverses: true), value: ...)` or `.phaseAnimator` |

**Rule:** start with `withAnimation`. Reach for `PhaseAnimator` only when you have 3+ ordered states. Reach for `KeyframeAnimator` only when you need parallel time-based tracks.

---

## Springs (the only easing you should care about)

SwiftUI ships named spring presets (iOS 17+): `.snappy`, `.bouncy`, `.smooth`, plus the parameterised
`.spring(duration:bounce:blendDuration:)` and `.interactiveSpring(...)`. Each of the three named ones
also takes `(duration:extraBounce:)` overloads. Use them. Tune `response` / `dampingFraction` only when
a preset is wrong.

The rest: https://github.com/AThevon/genjutsu/blob/HEAD/skills/_jutsu/swiftui-motion/SKILL.md