• The loops show that flexible hexagons contain two congruent tetrahedra, related by a rotation around a common diagonal (see manuscript, Theorem 9). The loops C6 (crowns) and C7 (stars) additionally show that in the case of rigid hexagons the tetrahedra are related by a reflection.
• Two perpendicular lines remain fixed in space: one contains the involved diagonal and the other the line segment between the midpoint of this diagonal and that of a non-ad­ja­cent side.

– It is recommended to open the context-menu (right-click or ctrl+click).
– To improve fast forward and backward movements, the animation should be downloaded.