Then, on a new layer, create the animation for the slingshot stretching back and then snapping forward to fire before snapping back again. You’ll want to start back in a “draw” position, as in the game the slingshot will be held ready until it fires at a click, so your “hold” keyframe at the start will stay that way—and only when the firing animation starts will it move.
The easiest way to do it is just to draw a simple rounded rectangle at the midpoint for your middle keyframe, and then copy that to your first keyframe and use the subselection tool to move the points of the shape around to distort it in the desired fashion. Then you can just duplicate the first keyframe on the last keyframe, and use a shape transformation to flip the graphic upside down so it’s positioned properly. Adding a shape tween between the keyframes will interpolate all of the positions in between. You shouldn’t have too many frames overall, as a snapping slingshot is very fast.
