met_document_addeventlistener.asp" class="underline">document event listener</a> to trigger the draw() function when mouse is <a href="https://developer.mozilla.org/en-US/docs/Web/Events/mousemove" class="underline">moved</a></li>
  <li>a <a href="http://www.w3schools.com/jsref/met_document_addeventlistener.asp" class="underline">document event listener</a> to trigger the setPosition() (user’s mouse current position) function when mouse is <a href="https://developer.mozilla.org/en-US/docs/Web/Events/mouse