Motion should explain state, preserve context, or reward intent. If it only delays the user, it is decoration. Useful movement helps an interface behave like one continuous place.
Start with the reason
Before animating, I ask what the user needs to understand. Did an item move? Did a layer appear? Did an action succeed? The answer determines direction, duration, and emphasis.
Timing creates character
Fast is not automatically better, and slow is not automatically premium. Frequent interactions should settle quickly; meaningful entrances can take a little more time. Performance changes perception, so I test transitions in the real layout rather than judging them only in a motion study.
The interface should remain understandable when every animation is removed.
Reduced-motion preferences are part of the design. The alternative can retain hierarchy and feedback while communicating the same change without unnecessary movement.
