Start with the arrival
Create at least two keys on the property you want to animate. Select the property name, choose Overshoot or Bounce, and click Apply.
Both behaviors use the property’s velocity just before each key. A quick arrival gives a stronger response. An arrival eased almost to a stop may produce very little motion. Try linear keys first when checking whether a behavior works.
If you select a whole layer, Springy chooses suitable keyed transforms. Select an exact property when you want to affect only one. The full selection rules cover separated Position and other numeric properties.
Spring past the key with Overshoot
Overshoot adds a decaying oscillation after a key. Use Bounce within its controls to set the amount, Settle to control how quickly it fades, and Speed to change the oscillation frequency.
Raise the amount for a looser spring. Raise Settle for a shorter tail. Faster oscillation also changes how far the spring travels, so judge amount and speed together in the comp.
The added motion resets from each arriving key. Leave time after the last key for the spring to settle.
Rebound from the key with Bounce
Bounce sends the value back against its incoming direction in shrinking hops. For a downward Position move that ends at a floor, the hops go back up.
Increase Height for stronger rebounds. Increase Gravity to make each hop return sooner.
On a move ending in a held value, Bounce rebounds from that endpoint. It does not detect other layers, surfaces, or collisions. If animation continues after the key, the rebound is added to that continuing keyed motion.
When the result is missing
Needs at least 2 keyframes means the property needs more keys. Has its own expression means Springy skipped an existing expression. See expression replacement before allowing an overwrite.
If the tool reports success but the motion looks unchanged, check arrival speed and the behavior’s amount control. Overshoot with Bounce at zero, or Bounce with Height at zero, adds no motion.