It would appear to be relatively simple yet very well executed.

It uses a bunch of still images which are revealed via a number of masks then there's certain colour transforms applied to various sections of the animation.

The simple lines of the spider web are animated on the 3D plane and tie in with the masks used of which some appear to animate 3 dimensionally as well.

Something like this should be easy to replicate but will be quite time consuming to do it with such finesse.

Does that help at all?