elite-accessibility（精英可达性）

Elite Accessibility

Making motion-rich websites accessible to everyone.

Quick Reference

Why This Matters

Motion can cause real harm:

• Vestibular disorders affect ~35% of adults over 40
• Motion sensitivity can trigger nausea, dizziness, migraines
• Cognitive overload - animations can distract users with ADHD or anxiety
• Seizure risk - flashing content can trigger photosensitive epilepsy

Accessibility isn't optional - it's a design requirement.

The Golden Rule

Every animation MUST have a prefers-reduced-motion alternative.

This is non-negotiable for elite web design.

Quick Implementation

CSS Approach

/* Global reduced motion */
@media (prefers-reduced-motion: reduce) {
  *,
  *::before,
  *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
    scroll-behavior: auto !important;
  }
}

GSAP Approach

// ALWAYS use gsap.matchMedia() for motion preferences
const mm = gsap.matchMedia();

mm.add('(prefers-reduced-motion: no-preference)', () => {
  // Full animations for users who want them
  gsap.from('.hero-content', {
    opacity: 0,
    y: 50,
    duration: 1,
    stagger: 0.2
  });
});

mm.add('(prefers-reduced-motion: reduce)', () => {
  // Instant state for users who prefer reduced motion
  gsap.set('.hero-content', { opacity: 1, y: 0 });
});

CSS Scroll-Driven Animations

/* Only enable scroll animations if motion is OK */
@media (prefers-reduced-motion: no-preference) {
  .scroll-animated {
    animation: reveal linear;
    animation-timeline: scroll();
  }
}

/* Fallback: just show the content */
@media (prefers-reduced-motion: reduce) {
  .scroll-animated {
    opacity: 1;
    transform: none;
  }
}

What to Provide Instead

Don't just disable animations - provide alternatives:

Example: Reveal Animation

const mm = gsap.matchMedia();

// Full experience
mm.add('(prefers-reduced-motion: no-preference)', () => {
  gsap.from('.card', {
    opacity: 0,
    y: 30,
    duration: 0.6,
    stagger: 0.1,
    scrollTrigger: {
      trigger: '.cards-section',
      start: 'top 80%'
    }
  });
});

// Reduced motion: simple fade, no movement
mm.add('(prefers-reduced-motion: reduce)', () => {
  gsap.from('.card', {
    opacity: 0,
    duration: 0.3,  // Shorter
    stagger: 0.05,  // Faster stagger
    scrollTrigger: {
      trigger: '.cards-section',
      start: 'top 80%'
    }
  });
});

Animation Guidelines

Safe Animations (Usually OK)

• Opacity changes (fade in/out)
• Small scale changes (0.95 → 1)
• Color transitions
• Short durations (< 300ms)

Problematic Animations (Need Alternatives)

• Large movements (sliding, flying)
• Parallax effects
• Zooming (in/out)
• Rotation
• Bouncing/pulsing
• Infinite loops

Dangerous (Avoid or Gate Heavily)

• Flashing/strobing (can cause seizures)
• Rapid movement
• Auto-playing video with motion
• Spinning elements

Testing Reduced Motion

macOS

System Preferences → Accessibility → Display → Reduce motion

Windows

Settings → Ease of Access → Display → Show animations in Windows (off)

iOS

Settings → Accessibility → Motion → Reduce Motion

Chrome DevTools

1. Open DevTools (F12)
2. Cmd/Ctrl + Shift + P → "Render"
3. Find "Emulate CSS media feature prefers-reduced-motion"

Contrast Quick Reference

WCAG Requirements

Quick Test

Use browser extensions:

• axe DevTools
• WAVE
• Stark

See wcag-contrast.md for detailed guidance.

Focus States

Every interactive element needs visible focus:

/* Base focus style */
:focus-visible {
  outline: 2px solid var(--color-accent);
  outline-offset: 2px;
}

/* Remove default, add custom */
button:focus {
  outline: none;
}

button:focus-visible {
  outline: 2px solid var(--color-accent);
  outline-offset: 2px;
  box-shadow: 0 0 0 4px rgba(37, 99, 235, 0.2);
}

See focus-keyboard.md for keyboard navigation patterns.

Screen Reader Considerations

Hide Decorative Animations

<!-- Decorative animation should be hidden -->
<div class="animated-background" aria-hidden="true"></div>

<!-- Content animations: ensure content is accessible -->
<div class="animated-card" role="article">
  <!-- Content here is accessible -->
</div>

Announce Dynamic Content

<!-- Live region for content that updates -->
<div aria-live="polite" aria-atomic="true">
  <p>Loading complete. Showing 12 results.</p>
</div>

Implementation Checklist

Every Animation Must:

• Check prefers-reduced-motion
• Provide reduced/no-motion alternative
• Not flash more than 3 times per second
• Not auto-play infinitely without user control
• Not cause layout shift that disrupts reading

Every Page Must:

• Pass WCAG AA contrast (4.5:1 for text)
• Have visible focus states
• Be keyboard navigable
• Work without JavaScript animations
• Have skip links for keyboard users

Resources

• MDN: prefers-reduced-motion
• WCAG 2.1 Guidelines
• A11y Project
• Inclusive Design Principles