         calipers.map({ self.styleCaliperView($0) })
         tracks.map({ self.styleTrackView($0) })
         
-        calipersAndTracks.map({ $0.alpha = 0 })
-        calipersAndTracks.map({ self.superview?.addSubview($0) })
+        (calipers + tracks).map({ $0.alpha = 0 })
+        (calipers + tracks).map({ self.superview?.addSubview($0) })
         
         resetCaliperRects()
     }

    private func finishTracking() {
        UIView.animateWithDuration(0.4, animations: { () -> Void in
            self.resetCaliperRects()
            self.calipersAndTracks.map({ $0.alpha = 0 })
        })
    }
}

    private var trackRect = CGRectZero
    private let calipers:[UIView]
    private let tracks:[UIView]
    
    //MARK: - Setup Etc.
    
    required init(coder aDecoder: NSCoder) {
        calipers = [leftCaliper, rightCaliper]
        tracks = [leftTrack, rightTrack]
        super.init(coder: aDecoder)
    }
    
