axiom-haptics

# Haptics & Audio Feedback

Comprehensive guide to implementing haptic feedback on iOS. Every Apple Design Award winner uses excellent haptic feedback - Camera, Maps, Weather all use haptics masterfully to create delightful, responsive experiences.

## Overview

Haptic feedback provides tactile confirmation of user actions and system events. When designed thoughtfully using the Causality-Harmony-Utility framework, axiom-haptics transform interfaces from functional to delightful.

This skill covers both simple haptics (`UIFeedbackGenerator`) and advanced custom patterns (`Core Haptics`), with real-world examples and audio-haptic synchronization techniques.

## When to Use This Skill

- Adding haptic feedback to user interactions
- Choosing between UIFeedbackGenerator and Core Haptics
- Designing audio-haptic experiences that feel unified
- Creating custom haptic patterns with AHAP files
- Synchronizing haptics with animations and audio
- Debugging haptic issues (simulator vs device)
- Optimizing haptic performance and battery impact

## System Requirements

- **iOS 10+** for UIFeedbackGenerator
- **iOS 13+** for Core Haptics (CHHapticEngine)
- **iPhone 8+** for Core Haptics hardware support
- **Physical device required** - haptics cannot be felt in Simulator

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## Part 1: Design Principles (WWDC 2021/10278)

Apple's audio and haptic design teams established three core principles for multimodal feedback:

### Causality - Make it obvious what caused the feedback

**Problem**: User can't tell what triggered the haptic
**Solution**: Haptic timing must match the visual/interaction moment

**Example from WWDC**:
- ✅ Ball hits wall → haptic fires at collision moment
- ❌ Ball hits wall → haptic fires 100ms later (confusing)

**Code pattern**:
```swift
// ✅ Immediate feedback on touch
@objc func buttonTapped() {
    let generator = UIImpactFeedbackGenerator(style: .medium)
    generator.impactOccurred()  // Fire immediately
    performAction()
}

// ❌ Delayed feedback lose