     
     internal static let EaseOutCirc = { (elapsed: NSTimeInterval, duration: NSTimeInterval) -> Double in
         var position = Double(elapsed / duration)
-        position--
+        position -= 1.0
         return Double( sqrt(1 - position * position) )
     }
     

        {
            return 0.5 * position * position
        }
        return -0.5 * ((--position) * (position - 2.0) - 1.0)
    }
    
    internal static let EaseInCubic = { (elapsed: NSTimeInterval, duration: NSTimeInterval) -> Double in

    
    internal static let EaseOutQuart = { (elapsed: NSTimeInterval, duration: NSTimeInterval) -> Double in
        var position = Double(elapsed / duration)
        position -= 1.0
        return -(position * position * position * position - 1.0)
    }
    
