title: particle brownian motion with directions
body: <p>I'm trying to use brownian motion to create a group of random moving particles.
  <a href="http://jsfiddle.net/J75Em/16/" rel="noreferrer">http://jsfiddle.net/J75Em/16/</a></p>
  
  <p>So far I've got the particles moving randomly but I'm not sure how to set the forward direction to make it look more natural. </p>
  
  <p>I've tried to use the change in x and y axis to calculate rotation using atan, you can see this by uncommenting rotate but this doesn't seem to perform well.</p>
  
  <p>Is this the right approach for this type of movement? thanks;</p>