Ease-in-out animations start slow, gain momentum toward the middle, then slow down again before stopping. Ease-in-out curves don’t have to be symmetrical, though.

Google’s Material Design recommends using an asymmetrical curve with faster easing in than easing out.^[1] Doing so accentuates animation and makes it look natural and responsive.

Not all objects in the real world move smoothly like easing curves do. So, there are two other types of motions you’ll want to master: the spring and the bounce.