Motion Principles

Motion Has Purpose

Every animation answers one of these questions:

1. Where did this come from? (spatial orientation)
2. What just happened? (state feedback)
3. What should I look at? (attention direction)
4. What's related? (grouping/connection)

If an animation doesn't answer any of these, remove it.

Timing

Duration Scale

• Micro-interactions (hover, toggle): 100-200ms
• Element transitions (fade, slide): 200-300ms
• Page transitions: 300-500ms
• Complex orchestrations: 500-800ms
• Loading/progress: match actual duration

The 300ms Rule

Most UI animations should be under 300ms. Users perceive anything longer as slow. The exception is orchestrated sequences where staggered delays create rhythm.

Easing

Which Curve When

• ease-out (decelerate): Elements entering the screen. They arrive and settle.
• ease-in (accelerate): Elements leaving the screen. They start slow and exit fast.
• ease-in-out: Elements moving between two visible positions.
• linear: Progress bars, loading spinners. Never for UI transitions.
• spring/bounce: Playful brands only. Subtle. Never on critical UI.

Custom Curves

/* Snappy entrance */
--ease-out-expo: cubic-bezier(0.16, 1, 0.3, 1);

/* Smooth move */
--ease-in-out-quart: cubic-bezier(0.76, 0, 0.24, 1);

/* Gentle settle */
--ease-out-quad: cubic-bezier(0.25, 0.46, 0.45, 0.94);

Stagger Patterns

When animating multiple items (list items, grid cards), stagger by 30-60ms per item. Cap total duration at 600ms (after ~10 items, start them together in groups).

Reduced Motion

Always respect prefers-reduced-motion. This is not optional.

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

Anti-Patterns

• Animations that block interaction (can't click until animation finishes)
• Parallax scrolling on mobile (performance killer, motion sickness trigger)
• Loading spinners when a skeleton screen would work
• Bounce effects on serious/professional products
• Animation on every single element (visual noise)