title: How to detect swipe direction between left/right and up/down
body: <p><strong>My Question:</strong> How do I detect when a user moves their finger up/down vs left/right (and how do I know which direction of those groups their finger moved)?</p>
  
  <p><strong>My Situation:</strong> I want to change the brightness of my app when they move their finger up and down (up = brighter, down = darker), and I want to switch between activities and/or views based on their left/right swipe.</p>