     private let animation: AnimationState -> Void
     private let id: String
     
-    init(id: String, duration: NSTimeInterval, animation: AnimationState -> Void) {
+    private init(id: String, duration: NSTimeInterval, animation: AnimationState -> Void) {
         self.start = NSDate()
         self.duration = duration
         self.animation = animation

// MARK: Implementation


private class PercentAnimator {
    
    private var animations: [Animation] = []
    

    }
}

private final class Animation {
    
    private let start: NSDate
    private let duration: NSTimeInterval
