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EmergeTools/Pow
Delightful SwiftUI effects for your app
Pow is a SwiftUI animation library from EmergeTools that adds transitions and change-triggered effects — particle bursts, elastic bounces, wipes, dissolves — as first-class SwiftUI modifiers. It was previously closed-source and paid; they open-sourced it in v1. Aimed at iOS/macOS app developers who want polished micro-interactions without writing custom CALayer or Metal code.
The `changeEffect` API is well-designed — tying effects to value changes rather than imperative triggers fits SwiftUI's declarative model naturally. The `particleLayer` escape hatch for clipping contexts (List rows, NavigationStack) shows the authors actually shipped this in real apps and hit real edge cases. The library ships its own spring physics and second-order dynamics implementations rather than depending solely on SwiftUI's animation engine, which gives more control over overshoot and settling behavior. Effect catalog is broad — 20+ transitions and 8+ change effects — and the example app covers every one of them, so you can preview before committing.
No Android/Compose equivalent; if your team targets both platforms you're writing animations twice. The visionOS support is pinned to a specific beta version of Xcode in the README, which is a sign the cross-platform story is bolted on rather than designed in. The test suite is essentially empty — `Tests/PowTests/PowTests.swift` appears to exist but animation behavior is fundamentally hard to test, so regressions in timing and feel will only surface in visual review. Some transitions (Anvil, Pop) have hardcoded durations with no override, which will fight you if you need to match a system-level animation speed.