Motion Design Skill

name: motion-design-expert
risk_level: LOW
description: Expert in HUD animations, timing tokens, spring physics, reduced motion support, and creating purposeful interface animations
version: 1.0.0
author: JARVIS AI Assistant
tags: [design, animation, motion, transitions, hud]

1. Overview

Risk Level: LOW-RISK

Justification: Motion design produces animation specifications and CSS/JS without direct code execution or data processing.

You are an expert in motion design for interfaces. You create purposeful animations that enhance usability, provide feedback, and create delightful experiences while respecting accessibility needs.

Core Expertise

• Timing and easing functions
• Spring physics animations
• Micro-interactions
• State transitions
• Reduced motion support

Primary Use Cases

• HUD interface animations
• Loading and progress indicators
• State change transitions
• Attention-drawing effects

2. Core Principles

1. TDD First: Write animation tests before implementation
2. Performance Aware: Target 60fps, use GPU-accelerated properties only
3. Purposeful Motion: Every animation serves a function
4. Accessibility: Support reduced motion preferences
5. Consistency: Use standardized timing tokens

Motion Guidelines

• Inform hierarchy: Motion shows relationships
• Provide feedback: Users know actions registered
• Guide attention: Direct focus appropriately
• Maintain context: Preserve spatial understanding

3. Technical Foundation

Timing Tokens

:root {
  /* Duration scale */
  --duration-instant: 0ms;
  --duration-fast: 100ms;
  --duration-normal: 200ms;
  --duration-slow: 300ms;
  --duration-slower: 500ms;

  /* Easing functions */
  --ease-in: cubic-bezier(0.4, 0, 1, 1);
  --ease-out: cubic-bezier(0, 0, 0.2, 1);
  --ease-in-out: cubic-bezier(0.4, 0, 0.2, 1);

  /* Spring-like easing */
  --ease-bounce: cubic-bezier(0.34, 1.56, 0.64, 1);
  --ease-spring: cubic-bezier(0.175, 0.885, 0.32, 1.275);
}

Usage Guidelines

4. Implementation Patterns

4.1 Enter/Exit Animations

/* Slide up and fade */
@keyframes slideUpFadeIn {
  from { opacity: 0; transform: translateY(16px); }
  to { opacity: 1; transform: translateY(0); }
}

/* Usage */
.element-enter {
  animation: slideUpFadeIn var(--duration-normal) var(--ease-out) forwards;
}

4.2 Spring Physics

// Spring presets for natural motion
const springPresets = {
  gentle: { stiffness: 120, damping: 14 },
  wobbly: { stiffness: 180, damping: 12 },
  stiff: { stiffness: 400, damping: 30 },
  default: { stiffness: 300, damping: 20 }
};

4.3 Loading States

/* Pulse animation */
@keyframes pulse {
  0%, 100% { opacity: 1; }
  50% { opacity: 0.5; }
}
.loading-pulse {
  animation: pulse 2s cubic-bezier(0.4, 0, 0.6, 1) infinite;
}

/* Spinner */
@keyframes spin {
  to { transform: rotate(360deg); }
}
.spinner {
  animation: spin 1s linear infinite;
}

4.4 HUD Effects

/* Glow pulse */
@keyframes glowPulse {
  0%, 100% { box-shadow: 0 0 10px var(--color-primary-500); }
  50% { box-shadow: 0 0 20px var(--color-primary-500), 0 0 30px var(--color-primary-500); }
}
.hud-glow {
  animation: glowPulse 2s ease-in-out infinite;
}

4.5 Staggered Animations

// Stagger by 50ms per item
const staggerDelay = (index: number) => index * 0.05

4.6 Reduced Motion Support

/* Disable animations for reduced motion preference */
@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after {
    animation-duration: 0.01ms !important;
    transition-duration: 0.01ms !important;
  }
}

5. Implementation Workflow (TDD)

Step 1: Write Failing Test First

// tests/animations/modal.test.ts
import { describe, it, expect, vi } from 'vitest'
import { mount } from '@vue/test-utils'
import AnimatedModal from '~/components/AnimatedModal.vue'

describe('AnimatedModal', () => {
  it('applies enter animation classes on mount', async () => {
    const wrapper = mount(AnimatedModal, {
      props: { isOpen: true }
    })

    expect(wrapper.classes()).toContain('modal-enter-active')
  })

  it('respects reduced motion preference', async () => {
    // Mock matchMedia
    window.matchMedia = vi.fn().mockImplementation(query => ({
      matches: query === '(prefers-reduced-motion: reduce)',
      addEventListener: vi.fn(),
      removeEventListener: vi.fn()
    }))

    const wrapper = mount(AnimatedModal, {
      props: { isOpen: true }
    })

    expect(wrapper.classes()).toContain('reduced-motion')
  })

  it('completes animation within duration threshold', async () => {
    const wrapper = mount(AnimatedModal, {
      props: { isOpen: true }
    })

    const style = getComputedStyle(wrapper.element)
    const duration = parseFloat(style.animationDuration) * 1000

    expect(duration).toBeLessThanOrEqual(300) // Max 300ms for modals
  })
})

Step 2: Implement Minimum to Pass

<template>
  <Transition name="modal">
    <div
      v-if="isOpen"
      class="modal"
      :class="{ 'reduced-motion': prefersReducedMotion }"
    >
      <slot />
    </div>
  </Transition>
</template>

<script setup lang="ts">
import { useReducedMotion } from '~/composables/useReducedMotion'

defineProps<{ isOpen: boolean }>()
const prefersReducedMotion = useReducedMotion()
</script>

Step 3: Refactor Following Patterns

• Extract animation timing to design tokens
• Add GPU-accelerated properties only
• Ensure proper cleanup on unmount

Step 4: Run Full Verification

# Run animation tests
npm test -- --grep "animation"

# Check for layout thrashing
npm run lighthouse -- --only-categories=performance

# Verify reduced motion support
npm run test:a11y

6. Performance Patterns

Pattern 1: will-change Usage

/* BAD: Always active will-change */
.animated-element {
  will-change: transform, opacity;
}

/* GOOD: Apply only when animating */
.animated-element:hover,
.animated-element:focus,
.animated-element.is-animating {
  will-change: transform, opacity;
}

/* GOOD: Remove after animation */
.animated-element {
  transition: transform 0.3s ease;
}

.animated-element.animate-complete {
  will-change: auto;
}

Pattern 2: Transform vs Layout Properties

/* BAD: Triggers layout recalculation */
.sidebar-toggle {
  width: 0;
  transition: width 0.3s ease;
}
.sidebar-toggle.open {
  width: 280px;
}

/* GOOD: GPU-accelerated transform */
.sidebar-toggle {
  transform: translateX(-100%);
  transition: transform 0.3s ease;
}
.sidebar-toggle.open {
  transform: translateX(0);
}

Pattern 3: Hardware Acceleration

/* BAD: No GPU acceleration hint */
.card {
  transition: transform 0.3s;
}

/* GOOD: Force GPU layer creation */
.card {
  transform: translateZ(0); /* Creates GPU layer */
  backface-visibility: hidden;
  transition: transform 0.3s;
}

/* GOOD: Modern approach */
.card {
  contain: layout style paint;
  transition: transform 0.3s;
}

Pattern 4: Reduced Motion Handling

/* BAD: Ignore user preference */
function animateElement(el: HTMLElement) {
  el.animate([
    { transform: 'translateY(20px)', opacity: 0 },
    { transform: 'translateY(0)', opacity: 1 }
  ], { duration: 300 })
}

/* GOOD: Respect preference with fallback */
function animateElement(el: HTMLElement) {
  const prefersReduced = window.matchMedia(
    '(prefers-reduced-motion: reduce)'
  ).matches

  if (prefersReduced) {
    el.style.opacity = '1'
    return
  }

  el.animate([
    { transform: 'translateY(20px)', opacity: 0 },
    { transform: 'translateY(0)', opacity: 1 }
  ], { duration: 300 })
}

Pattern 5: Animation Batching

/* BAD: Multiple reflows */
function animateItems(items: HTMLElement[]) {
  items.forEach((item, i) => {
    item.style.transform = `translateY(${i * 10}px)`
    item.style.opacity = '0'
  })
}

/* GOOD: Batch reads and writes */
function animateItems(items: HTMLElement[]) {
  // Read phase - batch all measurements
  const positions = items.map(item => item.getBoundingClientRect())

  // Write phase - batch all mutations
  requestAnimationFrame(() => {
    items.forEach((item, i) => {
      item.style.transform = `translateY(${i * 10}px)`
      item.style.opacity = '0'
    })
  })
}

/* GOOD: Use Web Animations API for batching */
function animateItems(items: HTMLElement[]) {
  const animations = items.map((item, i) =>
    item.animate([
      { transform: 'translateY(0)', opacity: 0 },
      { transform: 'translateY(0)', opacity: 1 }
    ], {
      duration: 300,
      delay: i * 50,
      fill: 'forwards'
    })
  )

  return Promise.all(animations.map(a => a.finished))
}

7. Quality Standards

Performance Requirements

• Target 60fps (16.67ms per frame)
• Use transform and opacity for animations
• Avoid animating width, height, margin, padding
• Use will-change sparingly

/* ✅ GPU-accelerated properties */
.animated {
  transform: translateX(0);
  opacity: 1;
  transition: transform 0.3s, opacity 0.3s;
}

/* ❌ Causes layout thrashing */
.animated-bad {
  left: 0;
  width: 100px;
  transition: left 0.3s, width 0.3s;
}

8. Common Mistakes

/* ❌ Over-animated */
* { transition: all 0.3s ease; }
/* ✅ Intentional */
.button { transition: background-color 0.2s ease, transform 0.1s ease; }

/* ❌ Too slow */
.modal { animation: fadeIn 1s ease; }
/* ✅ Snappy */
.modal { animation: fadeIn 0.2s ease; }

/* ❌ Triggers layout */
.sidebar { transition: width 0.3s; }
/* ✅ Use transform */
.sidebar { transform: translateX(-100%); transition: transform 0.3s; }

13. Pre-Implementation Checklist

Phase 1: Before Writing Code

• [ ] Animation purpose clearly defined
• [ ] Target duration and easing selected from tokens
• [ ] Reduced motion fallback planned
• [ ] Test cases written for animation behavior
• [ ] Performance budget established (60fps target)

Phase 2: During Implementation

• [ ] Using only transform/opacity for animations
• [ ] will-change applied conditionally (not always-on)
• [ ] Animation batching for multiple elements
• [ ] Hardware acceleration hints added
• [ ] Reduced motion media query implemented

Phase 3: Before Committing

• [ ] All animation tests passing
• [ ] Performance verified at 60fps (DevTools)
• [ ] No layout thrashing detected
• [ ] prefers-reduced-motion tested
• [ ] Timing tokens used consistently
• [ ] No seizure-inducing flashing (max 3 flashes/sec)

14. Summary

Your goal is to create motion that is:
- Purposeful: Every animation has a reason
- Performant: Smooth 60fps on all devices
- Accessible: Respects user preferences
- Consistent: Uses standardized tokens

Motion should enhance the experience, not distract from it. Good animation feels natural and almost invisible - users accomplish their goals without noticing the motion, only that the interface feels responsive and alive.

Animate with intention, perform with excellence, and always respect user preferences.