Flash Animation 2: Shape Tweening

With frame 48 selected, I'm going to pick the Rectangle Tool from the toolbar (next to the Oval Tool), and leave my stroke set to black while setting my fill to a violet shade. In about the same area where the circle was, we'll draw in a square (or rectangle, no need to try to set a perfect square). You can make yours any size, though I'm going to make mine significantly larger than my circle was. Once you've drawn your shape on this frame, the keyframe marker will instantly turn to black, indicating that there is an object on this keyframe.

Unlike motion tweens, shape tweens can only be performed on non-grouped shapes, or: shapes that have not been converted to symbols. So with your shape drawn, there's only a few more steps to go before we're ready to create the final animation.