It’s a shabby application of the smart rocket example. I think growing hair also follow certain kind of evaluation and selection to fit the environment(in this example is follow the arrow). For example, if you wear something on your head for a long time, it probably that the covered area will no longer grow hair and the hair of near area will grow to opposite direction to prevent the cover area.
P.S. most code is based on the original smart rocket example of NOC class.