title: Calculating degrees between 2 points with inverse Y axis
body: <p>I'm creating a simple 2D game in javascript/canvas.
  I need to figure out the angle of a certain object relative to my position.</p>
  
  <p>So: say I'm at (10,10) and the object is at (10,5) - that would result in 90 degrees (as positive Y is down, negative Y is up)
  (10,10) vs (10,15) would be 270 degrees.</p>
  
  <p>How would I go about this?</p>