title: using skphysicsBody and circle of radius to trap ball in circle
body: <p><img src="https://i.stack.imgur.com/UB1Is.png" alt="skphysics and "></p>
  
  <pre><code>    roundbg.physicsBody = SKPhysicsBody(circleOfRadius: round.frame.width/2)
      roundbg.physicsBody?.dynamic = false
  </code></pre>
  
  <p>Trying to trap the ball inside the circle(roundbg). The problem is that when I use circleOfRadius for my round texture it takes the whole circle and not just the border. I get why circleOfRadius is doing that but can't figure out how to grab just the border. Any ideas? So ideally when ball falls it gets trapped inside the circle(roundbg). </p>
  
  <p>First iOS app/game and very new to this. Thanks for you help!  </p>