UX Animation & Motion Skill

Animation system using Anime.js v4 for responsive, accessible UI motion. This skill covers animation patterns, timing, and reduced motion support.

Related Skills

• animejs-v4: Complete Anime.js 4.0 API reference
• js-micro-utilities: Array utilities like .at(-1) for accessing last element
• ux-iconography: Icon animation patterns
• ux-accessibility: Reduced motion requirements

Animation Import

import { animate } from 'animejs';

Note: Project uses import maps to resolve animejs to local node_modules.

Animation Utilities

The project provides reusable animations in js/utils/animations.js:

import {
  shake,
  pressEffect,
  successBounce,
  glow,
  DURATION,
  EASE
} from '../../utils/animations.js';

Duration Constants

const DURATION = {
  instant: 100,    // Micro-interactions
  quick: 200,      // Button press, toggles
  normal: 300,     // Standard transitions
  slow: 500,       // Page transitions
  celebration: 600 // Success animations
};

Easing Functions

const EASE = {
  snap: 'easeOutQuad',     // Quick, snappy feel
  smooth: 'easeInOutQuad', // Gentle transitions
  bounceOut: 'easeOutBack' // Playful, overshooting
};

Animation Patterns

Press Effect (Tactile Feedback)

For button clicks and taps:

pressEffect(element);
// or
animate(element, {
  scale: [1, 0.95, 1],
  duration: DURATION.instant,
  ease: EASE.snap
});

Success Bounce

For completed actions:

successBounce(element);
// or
animate(element, {
  scale: [1, 1.1, 1],
  duration: DURATION.normal,
  ease: EASE.bounceOut
});

Shake (Error/Invalid)

For validation failures:

shake(element, { intensity: 6 });
// or
animate(element, {
  translateX: [-6, 6, -6, 6, -3, 3, 0],
  duration: DURATION.normal,
  ease: EASE.snap
});

Glow Effect

For achievements or highlights:

glow(element, {
  color: 'rgba(74, 222, 128, 0.6)',
  intensity: 15
});
// Uses box-shadow animation

Pulse (Attention)

For elements requiring attention:

@keyframes pulse {
  0%, 100% { opacity: 1; }
  50% { opacity: 0.5; }
}

.attention {
  animation: pulse 1.5s ease-in-out infinite;
}

Transition Patterns

Fade In

animate(element, {
  opacity: [0, 1],
  duration: DURATION.normal,
  ease: EASE.smooth
});

Slide In

animate(element, {
  translateY: [20, 0],
  opacity: [0, 1],
  duration: DURATION.normal,
  ease: EASE.snap
});

Scale In

animate(element, {
  scale: [0.9, 1],
  opacity: [0, 1],
  duration: DURATION.quick,
  ease: EASE.bounceOut
});

Staggered List

animate('.list-item', {
  translateY: [20, 0],
  opacity: [0, 1],
  delay: (el, i) => i * 50,
  duration: DURATION.normal,
  ease: EASE.snap
});

State Change Animations

Attribute Change Response

attributeChangedCallback(name, oldVal, newVal) {
  if (name === 'completed' && newVal !== null) {
    this.#animateComplete();
  }
}

#animateComplete() {
  animate(this, {
    scale: [1, 2, 1],
    duration: DURATION.normal,
    ease: EASE.bounceOut
  });
}

Phase Transition

#animatePhaseChange() {
  animate(this.#container, {
    opacity: [1, 0, 1],
    duration: DURATION.slow,
    ease: EASE.smooth
  });
}

Game Feedback Animations

Word Completion

#celebrateWord() {
  successBounce(this.#wordElement);
  glow(this.#wordElement, { color: 'rgba(74, 222, 128, 0.6)' });
}

Score Update

#animateScore() {
  animate(this.#scoreElement, {
    scale: [1, 1.2, 1],
    duration: DURATION.quick,
    ease: EASE.bounceOut
  });
}

Achievement Unlock

#celebrateAchievement() {
  animate(this.#badge, {
    scale: [0, 1.2, 1],
    rotate: [0, -10, 10, 0],
    duration: DURATION.celebration,
    ease: EASE.bounceOut
  });
}

Reduced Motion Support

Check Preference

const prefersReducedMotion = window.matchMedia(
  '(prefers-reduced-motion: reduce)'
).matches;

if (!prefersReducedMotion) {
  animate(element, { scale: [1, 1.1, 1] });
} else {
  // Instant state change instead
  element.classList.add('completed');
}

CSS Fallback

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

Safe Animation Wrapper

function safeAnimate(element, props) {
  if (window.matchMedia('(prefers-reduced-motion: reduce)').matches) {
    // Apply final state immediately
    if (props.scale) element.style.transform = `scale(${props.scale.at(-1)})`;
    if (props.opacity) element.style.opacity = props.opacity.at(-1);
    return;
  }
  return animate(element, props);
}

CSS Transitions

For simple state changes, prefer CSS:

.button {
  transition:
    background-color 0.15s ease,
    transform 0.1s ease,
    opacity 0.15s ease;
}

.button:hover {
  background: var(--color-hover-overlay);
}

.button:active {
  transform: scale(0.98);
}

Loading Animations

Spinner

.spinner {
  width: 24px;
  height: 24px;
  border: 2px solid var(--theme-outline);
  border-top-color: var(--theme-primary);
  border-radius: 50%;
  animation: spin 0.6s linear infinite;
}

@keyframes spin {
  to { rotate: 360deg; }
}

Dots

.loading-dots span {
  animation: bounce 1s ease-in-out infinite;
}

.loading-dots span:nth-child(2) { animation-delay: 0.1s; }
.loading-dots span:nth-child(3) { animation-delay: 0.2s; }

@keyframes bounce {
  0%, 80%, 100% { transform: translateY(0); }
  40% { transform: translateY(-6px); }
}

Performance Guidelines

Do

• Use transform and opacity for smooth 60fps
• Keep animations under 300ms for interactions
• Use will-change sparingly for complex animations
• Cancel animations when element unmounts

Don't

• Animate width, height, margin, padding
• Use long durations for frequent interactions
• Chain many sequential animations
• Animate elements off-screen

Cleanup

#animation = null;

disconnectedCallback() {
  if (this.#animation) {
    this.#animation.pause();
    this.#animation = null;
  }
}

Animation Timing Reference

Action	Duration	Easing
Button press	100ms	easeOutQuad
Toggle switch	150ms	easeOutQuad
Dropdown open	200ms	easeOutQuad
Modal appear	200-300ms	easeOutBack
Page transition	300-500ms	easeInOutQuad
Success celebration	400-600ms	easeOutBack