Elite CSS Animations

Modern CSS animation capabilities - when JavaScript isn't needed.

Quick Reference

CSS vs GSAP Decision Guide

Use CSS When:

• Simple reveal/fade animations
• Progress indicators tied to scroll
• Hover/focus state transitions
• Performance is paramount (off-main-thread)
• Safari support isn't critical (for scroll-driven)
• You want to minimize JavaScript

Use GSAP When:

• Complex multi-element sequences
• Pin/sticky behavior needed
• Horizontal scrolling sections
• Cross-browser consistency critical
• Fine-grained control (scrub with snap)
• Timeline orchestration

Hybrid Approach

CSS for simple interactions, GSAP for complex sequences:

/* CSS: Hover states, simple transitions */
.card {
  transition: transform 0.3s ease, box-shadow 0.3s ease;
}
.card:hover {
  transform: translateY(-4px);
  box-shadow: 0 10px 30px rgba(0,0,0,0.15);
}

// GSAP: Complex scroll-driven sequences
gsap.timeline({
  scrollTrigger: { trigger: '.section', scrub: 1 }
})
.from('.title', { opacity: 0, y: 50 })
.from('.content', { opacity: 0 }, '-=0.3');

Browser Support (2026)

Scroll-Driven Animations Quick Start

/* Progress bar that fills as you scroll */
.progress-bar {
  transform-origin: left;
  transform: scaleX(0);
  animation: progress linear;
  animation-timeline: scroll();
}

@keyframes progress {
  to { transform: scaleX(1); }
}

/* Element reveals as it enters viewport */
@media (prefers-reduced-motion: no-preference) {
  .reveal {
    animation: fadeIn linear both;
    animation-timeline: view();
    animation-range: entry 0% cover 30%;
  }
}

@keyframes fadeIn {
  from { opacity: 0; transform: translateY(30px); }
  to { opacity: 1; transform: translateY(0); }
}

Safari Polyfill

<script src="https://flackr.github.io/scroll-timeline/dist/scroll-timeline.js"></script>

See scroll-driven-api.md for complete patterns.

View Transitions Quick Start

// Simple page transition
document.startViewTransition(() => {
  // Update the DOM
  updateContent();
});

/* Customize the transition */
::view-transition-old(root) {
  animation: fade-out 0.3s ease-out;
}

::view-transition-new(root) {
  animation: fade-in 0.3s ease-in;
}

@keyframes fade-out {
  to { opacity: 0; }
}

@keyframes fade-in {
  from { opacity: 0; }
}

See view-transitions.md for SPA integration.

@property Quick Start

Animate CSS custom properties that previously couldn't animate:

@property --progress {
  syntax: '<number>';
  initial-value: 0;
  inherits: false;
}

.progress-circle {
  --progress: 0;
  background: conic-gradient(
    var(--color-accent) calc(var(--progress) * 360deg),
    transparent 0
  );
  transition: --progress 1s ease-out;
}

.progress-circle.complete {
  --progress: 1;
}

See property-rule.md for gradient animations and more.

Visual Effects Quick Start

Clip-Path Reveal

.reveal {
  clip-path: inset(0 100% 0 0);
  transition: clip-path 0.6s cubic-bezier(0.4, 0, 0.2, 1);
}

.reveal.visible {
  clip-path: inset(0 0 0 0);
}

Backdrop Filter

.glass {
  backdrop-filter: blur(10px) saturate(180%);
  background: rgba(255, 255, 255, 0.7);
}

Mix Blend Mode

.text-overlay {
  mix-blend-mode: difference;
  color: white;
}

See visual-effects.md for creative patterns.

prefers-reduced-motion

Always wrap motion in preference checks:

/* Default: No animation */
.animated {
  opacity: 1;
  transform: none;
}

/* Only animate if user allows */
@media (prefers-reduced-motion: no-preference) {
  .animated {
    animation: fadeIn 0.6s ease-out;
  }
}

Performance Best Practices

Animate Only Compositor Properties

/* GOOD - GPU accelerated */
.card {
  transition: transform 0.3s, opacity 0.3s;
}

.card:hover {
  transform: translateY(-4px) scale(1.02);
  opacity: 0.9;
}

/* BAD - Triggers layout/paint */
.card:hover {
  width: 110%;
  margin-left: -5%;
  box-shadow: 0 10px 30px rgba(0,0,0,0.3);
}

Use will-change Sparingly

/* Apply only during animation */
.animating {
  will-change: transform, opacity;
}

/* Remove after animation */
.animation-complete {
  will-change: auto;
}

Contain Property

/* Isolate expensive effects */
.animated-section {
  contain: layout style paint;
}

Common Patterns

Smooth Hover Transitions

.card {
  transition:
    transform 0.3s cubic-bezier(0.4, 0, 0.2, 1),
    box-shadow 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

.card:hover {
  transform: translateY(-4px);
  box-shadow: 0 12px 24px rgba(0, 0, 0, 0.15);
}

Staggered Entrance

.item {
  opacity: 0;
  animation: fadeIn 0.5s ease forwards;
}

.item:nth-child(1) { animation-delay: 0.1s; }
.item:nth-child(2) { animation-delay: 0.2s; }
.item:nth-child(3) { animation-delay: 0.3s; }
/* ... or use CSS custom properties */

@keyframes fadeIn {
  to { opacity: 1; }
}

Loading Spinner

.spinner {
  width: 40px;
  height: 40px;
  border: 3px solid var(--color-border);
  border-top-color: var(--color-accent);
  border-radius: 50%;
  animation: spin 0.8s linear infinite;
}

@keyframes spin {
  to { transform: rotate(360deg); }
}

Resources

• MDN: CSS Animations
• MDN: Scroll-driven animations
• Chrome: View Transitions
• Cubic Bezier Generator