Motion should reduce confusion, not add polish

There is a test we apply to every animation before it ships: what question does this answer? If the answer is “none, it just looks nice”, it usually comes out.

Good interface motion does specific work. It shows where a panel came from, so the user knows how to get back. It confirms that a tap registered before the network responds. It maintains a sense of place while content changes underneath. In each case the motion is carrying information that would otherwise need a label or a loading message.

The practical upshot is that timing matters more than the effect. Anything over about 400ms starts to feel like waiting rather than responding, and anything that cannot be interrupted will eventually annoy someone trying to move quickly. We document durations and easing curves once, per project, and then apply them consistently — which is far less glamorous than it sounds, and far more effective.