Item — HN Reader

> what's the point of emphasizing the sliding?

Because the “knob” changes position. Like in the real world, objects can’t disappear in one place, and then instantly appear in another. Animating a UI state change in terms of a move transition can help people to understand how both end-states are logically connected to each other. The animation resembles the mechanics of the slider knob being a “perpetual entity” that can move between two positions, rather than the slider control as a whole being some sort of static icon that is instantly swapped out for another static icon once I click on it.

Whether or not animations are necessary might still be arguable. I suppose it depends on the complexity of the UI control, on personal preference, and certainly also on the general level of technical familiarity of the end-user.

I don't know about you but I probably wouldn't notice if my light switch suddenly moved to the opposite position instantly instead of in 50ms or something.

And animations wouldn't be quite as annoying if they actually were that fast.

You might not consciously observe how your light switch transitions to the opposite position, but I’d argue that most people still have an immediate and intuitive understanding of how both end-states of a light switch are related to them applying physical force onto the switch.

The toggle transition is supposed to resemble this notion, and aims to allow the user to build up an analogous mental model of cause and effect.

To me, this sounds like a valid and worthwhile idea in general. That animations are not always appropriate or fitting, or that they sometimes are laggy and sluggish, is a different story.