Give Motion a Clear Purpose

Choose a motion and describe the information it provides in one plain sentence. It might connect a selected object to its detail view, acknowledge a successful action or draw attention to newly available content. Distinguish that role from atmosphere or decoration. Both can be legitimate design choices, but they should be assessed differently. If you cannot explain what the movement contributes, compare the experience without it. The absence may reveal that a simpler transition communicates the same thing with less interruption to the user's task.

Look at the movement in the full sequence rather than as an isolated clip. Consider what the person is trying to do immediately before and after it, and whether the animation delays access to something they need. Mark the information that must remain clear even if the movement is shortened or removed. This gives later decisions about timing and fallback a stable purpose. The exercise is not to eliminate expression, but to make expression work with the task instead of requiring the user to wait for it.

Practice: Write one sentence explaining the purpose of three motions in an interface or title sequence.

Compare timing variants by changing one property at a time. Begin with the same start state, end state and path, then vary the duration and note how the movement feels in context. Next, compare easing while keeping duration stable. This makes it easier to explain which choice changes the perceived weight or emphasis. A small response to an action may need a different rhythm from a transition between scenes. Avoid choosing a value solely because it looked attractive in an unrelated reference or preset.

Write a short observation for each variant before deciding which one to keep. Describe whether it makes the change easier to follow, feels delayed, attracts too much attention or disappears before the relationship is understood. Test the variants as part of the actual interaction, including the time spent reading nearby content. Choose the timing that serves the stated purpose and record why. The resulting note is more useful to a collaborator than a number alone because it explains what should be preserved if implementation constraints require an adjustment.

Practice: Describe three timing variants of the same movement and choose one based on its purpose.

List the events that can happen before a motion finishes. A person may activate the control again, navigate away, change a setting or encounter a loading response. Decide whether each event should restart the motion, interrupt it, wait or show the final state immediately. These are behavior decisions, not finishing details. A transition that works only when actions happen in an ideal order can create confusing results during ordinary use, especially when the underlying content or network response arrives at an unexpected time.

Write the repeated-action and interrupted-action cases beside the main specification, using a simple sequence of events. For example, describe what should remain selected when a second item is chosen before the first transition ends. Check that the visible state still corresponds to the current action and that important controls do not become unusable unnecessarily. If you cannot decide a case from the design alone, name the question for the implementing team. Keeping it explicit is better than allowing different people to make incompatible assumptions.

Practice: Write what should happen if a user triggers the action twice or leaves halfway through.

Prepare the handoff as a description someone can implement without having attended the design review. Include the trigger, start and end states, changing properties, duration, easing, repetition and interruption rules. Link a visual reference when one exists, but do not rely on the reference to explain everything. Separate essential behavior from details that can vary. This helps the implementing team preserve the design's purpose when a technical constraint makes an exact visual match impractical or when a state needs additional handling.

Add a reduced-motion alternative that preserves the information rather than merely stating animation off. A selection still needs a clear visible state, and newly revealed content still needs an understandable reading order. Write a short acceptance checklist covering the ordinary sequence, one repeated action, one interruption and the fallback. Review these cases with the implementation, not only with the source animation. A complete handoff creates a shared description of behavior and makes it easier to identify whether a later difference is intentional, necessary or an unresolved problem.

Practice: Produce one motion specification with a static alternative and a short acceptance checklist.