title: How do neural networks use genetic algorithms and backpropagation to play games?
body: <p>I came across <a href="https://www.youtube.com/watch?v=u2t77mQmJiY" rel="noreferrer">this interesting video on YouTube on genetic algorithms</a>.</p>
  
  <p>As you can see in the video, the bots learn to fight.<br>
  Now, I have been studying neural networks for a while and I wanted to start learning genetic algorithms.. This somehow combines both. </p>
  
  <p>How do you combine genetic algorithms and neural networks to do this?<br>
  And also how does one know the error in this case which you use to back-propagate and update your weights and train the net? And also how do you think the program in the video calculated its fitness function ? I guess mutation is definitely happening in the program in the video but what about crossover ?</p>
  
  <p>Thanks!</p>