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

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

        {
            return 0.5 * position * position
        }
        
        return -0.5 * ((position - 1.0) * (position - 3.0) - 1.0)
    }
    
    internal static let EaseInCubic = { (elapsed: NSTimeInterval, duration: NSTimeInterval) -> Double in
