This animation  retraces, in main outlines, the discovery of the Cone, i.e., one of the two principal components in the geometric plan of the s.c. Cinderella engraving. The gif's opening scene features two circles, plus two symmetric arcs of  another circle (the Cone's Key, or Top-circle). The two arcs are symmetrical through their common centre, which means that when their ends are cross- connected by lines, those lines intersect at the circle's centre.
We could say that the circle unites both arcs. Next, a line is drawn to show that the centres of the three resulting circles form a straight line. This is the Cone's central axis.

 Drawing External Tangents To Two, or More Circles

A diameter of the top circle gets passed down to the bottom circle. Next, a line through the corresponding ends of the two parallel diameters intersects the central axis at the External Centre of Symmetry.
From that point we draw the external tangents to the circles, which just happens to work for the third circle, as well. The tangents just happen to disperse at 36°, just like the arms on a  five-pointed star.

 Drawing Internal Tangents Between Two Circles