     }
     
     fileprivate func drawBackgroundCircle(_ partial : Bool) {
-      let startAngle : CGFloat = CGFloat(M_PI) / CGFloat(2.0)
-      var endAngle : CGFloat = (2.0 * CGFloat(M_PI)) + startAngle
+      let startAngle : CGFloat = .pi / 2.0
+      var endAngle : CGFloat = (2.0 * .pi) + startAngle
       
       let center : CGPoint = CGPoint(x: self.bounds.size.width / 2, y: self.bounds.size.height / 2)
       let radius : CGFloat = (CGFloat(self.bounds.size.width) - CGFloat(self.lineWidth!)) / CGFloat(2.0)

      self.drawBackgroundCircle(true)
      
      let rotationAnimation : CABasicAnimation = CABasicAnimation(keyPath: "transform.rotation.z")
      rotationAnimation.toValue = NSNumber(value: M_PI * 2.0 as Double)
      rotationAnimation.duration = 1;
      rotationAnimation.isCumulative = true;
      rotationAnimation.repeatCount = HUGE;

      processBackgroundPath.lineWidth = CGFloat(self.lineWidth!)
      
      if (partial) {
        endAngle = (1.8 * .pi) + startAngle
      }
      
      processBackgroundPath.addArc(withCenter: center, radius: radius, startAngle: startAngle, endAngle: endAngle, clockwise: true)
