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:
Before
After
transform: scale(0)
transform: scale(0.95)
animation: fadeIn 400ms ease-in
animation: fadeIn 200ms ease-out
No reduced motion support
@media (prefers-reduced-motion: reduce)
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:
Is this element entering or exiting?
→ Use
ease-out
Is an on-screen element moving?
→ Use
ease-in-out
Is this a hover/color transition?
→ Use
ease
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
150
ms
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
200
ms
ease-out
;
}
.overlay
{
transition
:
opacity
200
ms
ease-out
;
}
Timing and Duration
Duration Guidelines
Element Type
Duration
Micro-interactions
100-150ms
Standard UI (tooltips, dropdowns)
150-250ms
Modals, drawers
200-300ms
Page transitions
300-400ms
Rule:
UI animations should stay under 300ms. Larger elements animate slower than smaller ones.
The Frequency Principle
Determine how often users will see the animation:
100+ times/day
→ No animation (or drastically reduced)
Occasional use
→ Standard animation
Rare/first-time
→ Can add delight
Example:
Raycast never animates its menu toggle because users open it hundreds of times daily.
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
200
ms
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.
Scenario
Solution
Make buttons feel responsive
Add
transform: scale(0.97)
on
:active
Element appears from nowhere
Start from
scale(0.95)
, not
scale(0)
Shaky/jittery animations
Add
will-change: transform
Hover causes flicker
Animate child element, not parent
Popover scales from wrong point
Set
transform-origin
to trigger location
Sequential tooltips feel slow
Skip delay/animation after first tooltip
Small buttons hard to tap
Use 44px minimum hit area (pseudo-element)
Something still feels off
Add subtle blur (under 20px) to mask it
Hover triggers on mobile
Use
@media (hover: hover) and (pointer: fine)
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