title: How do I train a neural net when I don't know the target?
body: <p>I'm making a neural network which learns to play flappy bird. The net receives:</p>
  
  <ol>
  <li>The distance (x) between the agent and the nearest pipe</li>
  <li>The distance (y) between the agent and the top of the nearest pipe</li>
  <li>The distance (y) between the agent and the bottom of the nearest pipe</li>
  </ol>
  
  <p>To train the neural net I need a desired output, which, obviously, is to safely clear the top and bottom of the pipe. However, how do I train the net if I don't know exactly how much the agent has to jump to do so?</p>
  
  <p>I'm new to neural nets, and I've written programs where the net can take a guess and I can compare that guess to the easily-calculatable correct answer, and I can adjust weights from there - in this case, I don't know the right answer, and the point of the net is to figure it out itself.</p>
  
  <p>What can I do to achieve this? Maybe a few links pointing me in the right direction?</p>
  
  <p>Thanks.</p>