Overshoot / anticipation

Two halves of the same idea. Anticipation is one of Disney's twelve principles of animation: the small move in the opposite direction before the real one, a card dipping 2px down before it lifts, a drawer nudging closed before it flies open. Overshoot is not on that list under its own name, but it is the physics the follow-through and settle principles describe: the element sails past its final value and comes back, which is what real mass does when it stops.

You get overshoot for free from a spring (low damping, and it naturally passes the target) or explicitly from back easing, a cubic-bezier whose control point goes outside the 0 to 1 range, like cubic-bezier(0.34, 1.56, 0.64, 1). Anticipation needs authoring: a keyframe at roughly 15 percent that moves the wrong way. Reach for both on things that should feel physical, like popovers, toggles, buttons, and drag-release.

Gotcha: overshoot on anything large or text-heavy reads as a rendering bug, not personality. Keep it to transform and small elements, cap the overshoot around 3 to 8 percent, and never overshoot a property that has no meaningful 'past' (opacity above 1, a color, a clipped panel edge). Anticipation also costs perceived latency, so skip it on anything that responds to a direct tap.