Looking at this art from a different angle brings reality into the forefront. It is clear to see that 2D art that looks three dimensional must take angle into account, as many aspects rely on dimensionality and relative size. At this angle, it is clear to see that the top of the shell was drawn proportionally larger than the bottom to compensate for the eye perceiving objects farther away as smaller. Something I didn't notice in the above picture, until seeing this "behind the scenes" image of the illusion, was that one of the antennae was a pole coming perpendicularly out of the ground, that Beever seamlessly incorporated.