Web Animation Design

Web Animation Design

A comprehensive guide for creating animations that feel right, based on Emil Kowalski's "Animations on the Web" course.

Initial Response

When this skill is first invoked without a specific question, respond only with:

I'm ready to help you with animations based on Emil Kowalski's animations.dev course.

Do not provide any other information until the user asks a question.

Review Format (Required)

When reviewing animations, you MUST use a markdown table. Do NOT use a list with "Before:" and "After:" on separate lines. Always output an actual markdown table like this:

Wrong format (never do this):

Before: transform: scale(0)
After: transform: scale(0.95)
────────────────────────────
Before: 400ms duration
After: 200ms

Correct format: A single markdown table with | Before | After | columns, one row per issue.

Quick Start

Every animation decision starts with these questions:

1. Is this element entering or exiting? → Use ease-out 2. Is an on-screen element moving? → Use ease-in-out 3. Is this a hover/color transition? → Use ease 4. Will users see this 100+ times daily? → Don't animate it

The Easing Blueprint

ease-out (Most Common)

Use for user-initiated interactions: dropdowns, modals, tooltips, any element entering or exiting the screen.

/* Sorted weak to strong */
--ease-out-quad: cubic-bezier(0.25, 0.46, 0.45, 0.94);
--ease-out-cubic: cubic-bezier(0.215, 0.61, 0.355, 1);
--ease-out-quart: cubic-bezier(0.165, 0.84, 0.44, 1);
--ease-out-quint: cubic-bezier(0.23, 1, 0.32, 1);
--ease-out-expo: cubic-bezier(0.19, 1, 0.22, 1);
--ease-out-circ: cubic-bezier(0.075, 0.82, 0.165, 1);

Why it works: Acceleration at the start creates an instant, responsive feeling. The element "jumps" toward its destination then settles in.

ease-in-out (For Movement)

Use when elements already on screen need to move or morph. Mimics natural motion like a car accelerating then braking.

/* Sorted weak to strong */
--ease-in-out-quad: cubic-bezier(0.455, 0.03, 0.515, 0.955);
--ease-in-out-cubic: cubic-bezier(0.645, 0.045, 0.355, 1);
--ease-in-out-quart: cubic-bezier(0.77, 0, 0.175, 1);
--ease-in-out-quint: cubic-bezier(0.86, 0, 0.07, 1);
--ease-in-out-expo: cubic-bezier(1, 0, 0, 1);
--ease-in-out-circ: cubic-bezier(0.785, 0.135, 0.15, 0.86);

ease (For Hover Effects)

Use for hover states and color transitions. The asymmetrical curve (faster start, slower end) feels elegant for gentle animations.

transition: background-color 150ms ease;

linear (Avoid in UI)

Only use for:

• Constant-speed animations (marquees, tickers)
• Time visualization (hold-to-delete progress indicators)

Linear feels robotic and unnatural for interactive elements.

ease-in (Almost Never)

Avoid for UI animations. Makes interfaces feel sluggish because the slow start delays visual feedback.

Paired Elements Rule

Elements that animate together must use the same easing and duration. Modal + overlay, tooltip + arrow, drawer + backdrop—if they move as a unit, they should feel like a unit.

/* Both use the same timing */
.modal {
  transition: transform 200ms ease-out;
}
.overlay {
  transition: opacity 200ms ease-out;
}

Timing and Duration

Duration Guidelines

Rules:

• UI animations should stay under 300ms
• Larger elements animate slower than smaller ones
• Exit animations can be ~20% faster than entrance
• Match duration to distance - longer travel = longer duration

The Frequency

Determine how often users will see the animation:

• 100+ times/day → No animation (or drastically reduced)
• Occasional use → Standard animation
• Rare/first-time → Can be more special

Example: Raycast never animates because users open it hundreds of times a day.

When to Animate

Do animate:

• Enter/exit transitions for spatial consistency
• State changes that benefit from visual continuity
• Responses to user actions (feedback)
• Rarely-used interactions where delight adds value

Don't animate:

• Keyboard-initiated actions
• Hover effects on frequently-used elements
• Anything users interact with 100+ times daily
• When speed matters more than smoothness

Marketing vs. Product:

• Marketing: More elaborate, longer durations allowed
• Product: Fast, purposeful, never frivolous

Spring Animations

Springs feel more natural because they don't have fixed durations—they simulate real physics.

When to Use Springs

• Drag interactions with momentum
• Elements that should feel "alive" (Dynamic Island)
• Gestures that can be interrupted mid-animation
• Organic, playful interfaces

Configuration

Apple's approach (recommended):

// Duration + bounce (easier to understand)
{ type: "spring", duration: 0.5, bounce: 0.2 }

Traditional physics:

// Mass, stiffness, damping (more complex)
{ type: "spring", mass: 1, stiffness: 100, damping: 10 }

Bounce Guidelines

• Avoid bounce in most UI contexts
• Use bounce for drag-to-dismiss, playful interactions
• Keep bounce subtle (0.1-0.3) when used

Interruptibility

Springs maintain velocity when interrupted—CSS animations restart from zero. This makes springs ideal for gestures users might change mid-motion.

Performance

The Golden Rule

Only animate transform and opacity. These skip layout and paint stages, running entirely on the GPU.

Avoid animating:

• padding, margin, height, width (trigger layout)
• blur filters above 20px (expensive, especially Safari)
• CSS variables in deep component trees

Optimization Techniques

/* Force GPU acceleration */
.animated-element {
  will-change: transform;
}

React-specific:

• Animate outside React's render cycle when possible
• Use refs to update styles directly instead of state
• Re-renders on every frame = dropped frames

Framer Motion:

// Hardware accelerated (transform as string)
<motion.div animate={{ transform: "translateX(100px)" }} />

// NOT hardware accelerated (more readable)
<motion.div animate={{ x: 100 }} />

CSS vs. JavaScript

• CSS animations run off main thread (smoother under load)
• JS animations (Framer Motion, React Spring) use requestAnimationFrame
• CSS better for simple, predetermined animations
• JS better for dynamic, interruptible animations

Accessibility

Animations can cause motion sickness or distraction for some users.

prefers-reduced-motion

Whenever you add an animation, also add a media query to disable it:

.modal {
  animation: fadeIn 200ms ease-out;
}

@media (prefers-reduced-motion: reduce) {
  .modal {
    animation: none;
  }
}

Reduced Motion Guidelines

• Every animated element needs its own prefers-reduced-motion media query
• Set animation: none or transition: none (no !important)
• No exceptions for opacity or color - disable all animations
• Show play buttons instead of autoplay videos

Framer Motion Implementation

import { useReducedMotion } from "framer-motion";

function Component() {
  const shouldReduceMotion = useReducedMotion();

  return (
    <motion.div
      initial={shouldReduceMotion ? false : { opacity: 0, y: 20 }}
      animate={{ opacity: 1, y: 0 }}
    />
  );
}

Touch Device Considerations

/* Disable hover animations on touch devices */
@media (hover: hover) and (pointer: fine) {
  .element:hover {
    transform: scale(1.05);
  }
}

Touch devices trigger hover on tap, causing false positives.

Practical Tips

Quick reference for common scenarios. See PRACTICAL-TIPS.md for detailed implementations.

Easing Decision Flowchart

Is the element entering or exiting the viewport? ├── Yes → ease-out └── No ├── Is it moving/morphing on screen? │ └── Yes → ease-in-out └── Is it a hover change? ├── Yes → ease └── Is it constant motion? ├── Yes → linear └── Default → ease-out

Reference Files

• PRACTICAL-TIPS.md - Detailed implementations for common animation scenarios

---

Practical Animation Tips

Detailed reference guide for common animation scenarios. Use this as a checklist when implementing animations.

Recording & Debugging

Record Your Animations

When something feels off but you can't identify why, record the animation and play it back frame by frame. This reveals details invisible at normal speed.

Fix Shaky Animations

Elements may shift by 1px at the start/end of CSS transform animations due to GPU/CPU rendering handoff.

Fix:

.element {
  will-change: transform;
}

This tells the browser to keep the element on the GPU throughout the animation.

Take Breaks

Don't code and ship animations in one sitting. Step away, return with fresh eyes. The best animations are reviewed and refined over days, not hours.

Button & Click Feedback

Scale Buttons on Press

Make interfaces feel responsive by adding subtle scale feedback:

button:active {
  transform: scale(0.97);
}

This gives instant visual feedback that the interface is listening.

Don't Animate from scale(0)

Starting from scale(0) makes elements appear from nowhere—it feels unnatural.

Bad:

.element {
  transform: scale(0);
}
.element.visible {
  transform: scale(1);
}

Good:

.element {
  transform: scale(0.95);
  opacity: 0;
}
.element.visible {
  transform: scale(1);
  opacity: 1;
}

Elements should always have some visible shape, like a deflated balloon.

Tooltips & Popovers

Skip Animation on Subsequent Tooltips

First tooltip: delay + animation. Subsequent tooltips (while one is open): instant, no delay.

.tooltip {
  transition:
    transform 125ms ease-out,
    opacity 125ms ease-out;
  transform-origin: var(--transform-origin);
}

.tooltip[data-starting-style],
.tooltip[data-ending-style] {
  opacity: 0;
  transform: scale(0.97);
}

/* Skip animation for subsequent tooltips */
.tooltip[data-instant] {
  transition-duration: 0ms;
}

Radix UI and Base UI support this pattern with data-instant attribute.

Make Animations Origin-Aware

Popovers should scale from their trigger, not from center.

/* Default (wrong for most cases) */
.popover {
  transform-origin: center;
}

/* Correct - scale from trigger */
.popover {
  transform-origin: var(--transform-origin);
}

Radix UI:

.popover {
  transform-origin: var(--radix-dropdown-menu-content-transform-origin);
}

Base UI:

.popover {
  transform-origin: var(--transform-origin);
}

Speed & Timing

Keep Animations Fast

A faster-spinning spinner makes apps feel faster even with identical load times. A 180ms select animation feels more responsive than 400ms.

Rule: UI animations should stay under 300ms.

Don't Animate Keyboard Interactions

Arrow key navigation, keyboard shortcuts—these are repeated hundreds of times daily. Animation makes them feel slow and disconnected.

Never animate:

• List navigation with arrow keys
• Keyboard shortcut responses
• Tab/focus movements

Be Careful with Frequently-Used Elements

A hover effect is nice, but if triggered multiple times a day, it may benefit from no animation at all.

Guideline: Use your own product daily. You'll discover which animations become annoying through repeated use.

Hover States

Fix Hover Flicker

When hover animation changes element position, the cursor may leave the element, causing flicker.

Problem:

.box:hover {
  transform: translateY(-20%);
}

Solution: Animate a child element instead:

<div class="box">
  <div class="box-inner"></div>
</div>

.box:hover .box-inner {
  transform: translateY(-20%);
}

.box-inner {
  transition: transform 200ms ease;
}

The parent's hover area stays stable while the child moves.

Disable Hover on Touch Devices

Touch devices don't have true hover. Accidental finger movement triggers unwanted hover states.

@media (hover: hover) and (pointer: fine) {
  .card:hover {
    transform: scale(1.05);
  }
}

Note: Tailwind v4's hover: class automatically applies only when the device supports hover.

Touch & Accessibility

Ensure Appropriate Target Areas

Small buttons are hard to tap. Use a pseudo-element to create larger hit areas without changing layout.

Minimum target: 44px (Apple and WCAG recommendation)

@utility touch-hitbox {
  position: relative;
}

@utility touch-hitbox::before {
  content: "";
  position: absolute;
  display: block;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
  width: 100%;
  height: 100%;
  min-height: 44px;
  min-width: 44px;
  z-index: 9999;
}

Usage:

<button className="touch-hitbox">
  <BellIcon />
</button>

Easing Selection

Use ease-out for Enter/Exit

Elements entering or exiting should use ease-out. The fast start creates responsiveness.

.dropdown {
  transition:
    transform 200ms ease-out,
    opacity 200ms ease-out;
}

ease-in starts slow—wrong for UI. Same duration feels slower because the movement is back-loaded.

Use ease-in-out for On-Screen Movement

Elements already visible that need to move should use ease-in-out. Mimics natural acceleration/deceleration like a car.

.slider-handle {
  transition: transform 250ms ease-in-out;
}

Use Custom Easing Curves

Built-in CSS curves are usually too weak. Custom curves create more intentional motion.

Resources:

• Course reference: /learn/easing-curves
• External: easings.co

Visual Tricks

Use Blur as a Fallback

When easing and timing adjustments don't solve the problem, add subtle blur to mask imperfections.

.button-transition {
  transition:
    transform 150ms ease-out,
    filter 150ms ease-out;
}

.button-transition:active {
  transform: scale(0.97);
  filter: blur(2px);
}

Blur bridges visual gaps between states, tricking the eye into seeing smoother transitions. The two states blend instead of appearing as distinct objects.

Performance note: Keep blur under 20px, especially on Safari.

Why Details Matter

"All those unseen details combine to produce something that's just stunning, like a thousand barely audible voices all singing in tune."

— Paul Graham, Hackers and Painters

Details that go unnoticed are good—users complete tasks without friction. Great interfaces enable users to achieve goals with ease, not to admire animations.