Wha'? Who? How In The...?

Milk's "Brittleactica" site is absolutely one of the most fun, and easiest to navigate flash sites out there. I know its kinda old now, and I am behind the times I guess (in this business if you don't keep up, you getting beaten down...)But I am still at a loss as to how to do it?? Any hints anyone? Closest I can figure is they render in 3D platform of choice, edit, and make Flash Movie, imbed on lower layer and upper layer add in inviso buttons that track the planet they want. So far so good. But how in the great multiverse do they get it to be interactive with the position of the planets respective to their neighbors... I baffled (not uncommon).