A shape turns into another shape only because something happened to it: the sack ends as the tower's outline because it caught what fell.
Every body is one closed pen line with exactly 64 points, and point i is the same anatomical place in every drawing: point 0 is the middle of the bottom, 22 and 42 are the two corners, 32 is the middle of the top. I drew 22 contour keys for the sack, 7 for the tower and its pile, and one rigid knife outline; the full sack's last key is the uncut tower's own outline with its two corners tied up, and the fallen pile's two humps sit at the same indices as the sack's corners.
Each frame is a weighted blend of two keys' corresponding points, paced by the score, followed by one vertical rescale about the table that holds the drawn area at its flour budget; the corner points are blended from the pose three frames earlier, so they trail. Travel along the table comes only from a planted bottom corner (the body inches forward by pulling its other corner up to it) or from a parabola while airborne, and in the gather the pile's outline is lifted and blended point-for-point into the sack's outline as the pile loses the area the sack gains. The tower's lean is not keyed: each frame it takes the smaller of its free-fall lean and the angle at which its face meets the sack's drawn points, so the sack's contour is what holds it; the penny slides off the tilting top under friction and falls at 9.8 m/s² until it meets the sack's top line.
| choice | score | measured |
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Area is the drawn area of the closed contour in square metres, and it is the film's measure of flour. The two slices cut in Act 1 topple, break into their own outline's strokes and settle off the plate as dust; their area equals the flour the sack already holds, so the sack's full outline equals the uncut tower.