     :returns: An SKShader that will produce a sweep gradient. Note: the current implementation simply uses the GLSL mix function, which is a linear interpolation. For colors near to each other on the spectrum the results are fine; for very different colors the results can be pretty ugly. If you need a gradient between very different colors then you can simply add more clors in between to narrow the relative distances.
     
     */
-    func sweepGradientShader(#colors: [UIColor], locations: [CGFloat]?, center: CGPoint?, startAngle: Float?, blended: Bool, keepShape: Bool) -> SKShader {
+    private func sweepGradientShader(#colors: [UIColor], locations: [CGFloat]?, center: CGPoint?, startAngle: Float?, blended: Bool, keepShape: Bool) -> SKShader {
         
         
         // Sanitization

    
    private let u_startAngle = SKUniform(name: "u_startAngle", float: 0.0)
    
    /// startAngle is an angle in radians between 0 and 2Pi, where 0 is to the right along the x axis. Red will start at this angle. Default is 0.
    var startAngle : Float = 0.0 {
        didSet {
            u_startAngle.floatValue = (startAngle / Float(2 * M_PI)) % Float(1.0)
        }
    }
    


    
    // MARK: Linear Gradient

    /**
    
    A SKSpriteNode with a linear gradient from bottom to top in the given texture.
