Rocketmagnet

Looking at the examples and the documentation, I see it's possible to train a neural network on some fixed data set. However, I would like to use a fitness function to train my NN. Is this possible? For example, if I wanted to make a NN to drive a toy car based on sensor inputs, I can't possible provide a set of training data, all I can do is judge how far the NN managed to drive the car. So, is it possible to train based on a fitness function? Many thanks Hugo