 
     // MARK: - Properties
 
-    let EAGLContext: OpenGLES.EAGLContext
+    private let EAGLContext: OpenGLES.EAGLContext
+    private let GLKView: GLKit.GLKView
+    private let CIContext: CoreImage.CIContext
 
-    let GLKView: GLKit.GLKView
-    
-    let CIContext: CoreImage.CIContext
-
+    /// The corresponding annotation.
     var annotation: BlurAnnotation? {
         didSet {
             setNeedsDisplay()

            }
        }
    }

    override var annotationFrame: CGRect? {
        return annotation?.frame
    }
    
    var touchTargetFrame: CGRect? {
        guard let annotationFrame = annotationFrame else { return nil }
        
        let size = frame.size

        }
    }
    
    /// Whether to draw a border on the blur view.
    var drawsBorder = false {
        didSet {
            if drawsBorder != oldValue {
