Basically it looks like the center of the vine is hollow and inverted, and the programming decides which side to feed more or less to to make it turn, and then

Basically it looks like the center of the vine is hollow and inverted, and the programming decides which side to feed more or less to to make it turn, and then air is added to create stability. If you can imagine bunching up a longer sock to put it on, it's a little like that.