Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
npx skills add existential-birds/beagle --skill ios-animation-implementationgit clone --depth 1 https://github.com/existential-birds/beagleWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/skills/existential-birds/beagle/ios-animation-implementation)<a href="https://agentmods.dev/skills/existential-birds/beagle/ios-animation-implementation"><img src="https://agentmods.dev/badge/skills/existential-birds/beagle/ios-animation-implementation/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/skills/existential-birds/beagle/ios-animation-implementation"><img src="https://agentmods.dev/badge/skills/existential-birds/beagle/ios-animation-implementation.svg" alt="Reviewed on agentmods" width="80" height="20"></a>What it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00108 | $0.01958 |
| Opus 5.5 | $0.00043 | $0.00783 |
| Sonnet 5.5 | $0.00022 | $0.00392 |
| Haiku 4.5 | $0.00011 | $0.00196 |
Grade A, and why
ios-animation-implementation scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 1mo ago.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
How it starts
The opening of the file, as written. The whole thing — 132 lines — stays where its author put it; the contents beside it link to each section on GitHub.
iOS Animation Implementation
Write animation code that uses Apple's frameworks directly. Third-party animation libraries add dependency risk and often lag behind new OS releases — Apple's APIs are well-optimized for the render pipeline and get free improvements with each iOS version.
Before Writing Custom Animation
Check whether the system already handles the motion you need. Apple's HIG: "Many system components automatically include motion, letting you offer familiar and consistent experiences throughout your app." System components also automatically adjust for accessibility settings and input methods — Liquid Glass (iOS 26) responds with greater emphasis to direct touch and produces subdued effects for trackpad. Custom animation can't match this adaptiveness for free, so prefer system-provided motion when it exists.
Skip custom animation when:
- Standard navigation transitions cover your case (push, pop, sheet, fullScreenCover)
- SF Symbol
.symbolEffectprovides the feedback you need .contentTransition(.numericText)handles your data change- The system's default spring on
withAnimationis sufficient
Write custom animation when:
- The system doesn't provide the spatial relationship you need (hero transitions, custom gestures)
- You need coordinated multi-property choreography
- The animation is a signature moment that defines the app's identity
- Gesture-driven interaction requires custom progress mapping
API Selection
Choose the right API for the job. Start with SwiftUI animations (simplest, most declarative), drop to UIKit when you need interactive control, and reach for Core Animation only when you need layer-level precision.
| Need | API | Why |
|---|---|---|
| State-driven property changes | withAnimation / .animation(_:value:) |
Declarative, automatic interpolation |
| Multi-step sequenced animation | PhaseAnimator |
Discrete phases with per-phase timing |
| Per-property timeline control | KeyframeAnimator |
Independent keyframe tracks per property |
| Hero transitions between views | matchedGeometryEffect + Namespace |
Geometry matching across view identity |
| Navigation push/pop with zoom | .navigationTransition(.zoom) |
iOS 18+ built-in zoom transition |
| Custom view insertion/removal | Transition protocol conformance |
TransitionPhase-based modifier |
| In-view content swap | .contentTransition() |
Numeric text, interpolation, opacity |
| Scroll-position-based effects | .scrollTransition |
Phase-driven scroll-linked animation |
| SF Symbol animation | .symbolEffect() |
Bounce, pulse, wiggle, breathe, rotate |
| Interactive/interruptible (UIKit) | UIViewPropertyAnimator |
Pause, resume, reverse, scrub |
| Per-layer property animation | CABasicAnimation / CASpringAnimation |
Shadow, border, cornerRadius animation |
| Complex choreography (layers) | CAKeyframeAnimation + CAAnimationGroup |
Multi-property layer animation |
| Physics simulation | UIDynamicAnimator |
Gravity, collision, snap, attachment |
| Haptic feedback paired with animation | .sensoryFeedback modifier |
Tied to value changes |
| Animated background gradients | MeshGradient |
2D grid of positioned, animated colors |
What ships with it
4 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.
What this file has done since we first saw it
Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.
- 1mo ago First seen · 132 lines · 108 tokens per session scan A 51341ff4aa32
ios-animation-implementation is a skill published in the GitHub repository existential-birds/beagle (82 stars, last pushed 1mo ago), licensed Apache-2.0. It adds 108 tokens to every session and 1,958 once invoked, about $0.0004 per session on Opus 5.5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-09-16.
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