# jwilling/JNWSpringAnimation

Spring physics for Core Animation.

Repository: https://github.com/jwilling/JNWSpringAnimation
Canonical: https://ross.abutalabs.com/products/jnwspringanimation
Language: Objective-C
License: MIT
License Family: permissive
Last push: 2017-05-31T09:43:00+00:00

## Health v2 (maintenance only)
Score: 32/100 (v2, computed 2026-09-03T02:20:16.233290+00:00)
- activity 0, release rhythm 35, longevity 100
- inputs: {"age_days": 4840, "days_push": 3381, "days_rel": null, "gap_med": null, "n_releases_24m": 0}
- flags: no_releases
- formula: round(0.45*activity + 0.35*rhythm + 0.20*longevity); archived -> min(score, 10)

## Adoption (not part of the score)
Stars 1007, forks 63 (observed 2026-08-28T04:03:12.361607+00:00)

## What it is
An Objective-C library that subclasses CAKeyframeAnimation to provide spring physics (damped harmonic) animations for Core Animation layers on iOS and macOS. It serves as an open-source alternative to the private CASpringAnimation, with configurable stiffness, damping, and mass.

## Use cases
- add spring physics animations to iOS UI elements
- animate CALayer properties with damped harmonic motion
- replace the private CASpringAnimation with an open-source equivalent
- create natural bounce effects for view transitions
- tune stiffness, damping, and mass for custom animation feel
- make iOS apps feel more physical and responsive

## When to choose
- you need spring-based Core Animation animations in an Objective-C or Swift iOS/macOS app
- you want fine control over spring constants like stiffness, damping, and mass
- you're targeting older iOS versions before CASpringAnimation was public

## When to avoid
- you're on modern iOS where the built-in CASpringAnimation or UIView spring APIs suffice
- you need velocity-based spring animations, which this library does not implement
- you need a maintained library with active support - the last release was in 2017

## Facets
- artifact type: library
- maturity: maintenance
- function: animation
- domain: mobile-development, graphics
- platform: cpp
- tags: core-animation, spring-physics, objective-c, uikit, damped-harmonic-motion, ios, macos, swift

## Member repositories
- jwilling/JNWSpringAnimation (main) score 32

## Provenance
- Observed fields: from GitHub, fetched 2026-08-28T04:03:12.361607+00:00.
- Health v2: computed from the inputs above; adoption is never an input.
- Inferred fields (summary, facets, guidance): AI-extracted, prompt v1, taxonomy v1, on 2026-08-30T07:12:27.306267+00:00, confidence not recorded.
  - readme: https://github.com/jwilling/JNWSpringAnimation (fetched 2026-08-28T04:03:12.361607+00:00, sha da0cbee7062c)
- Data as of 2026-08-30T08:39:29.467469+00:00.