         }
     }
     
-    func addDraggable(initialLocation location: CGPoint, radius: CGFloat) -> Draggable {
+    func addDraggable(initialLocation location: CGPoint, radius: CGFloat) {
         let draggable = Draggable(initialLocation: location, radius: radius)
         draggable.delegate = self
         self.draggables.append(draggable)
-        return draggable
     }
     
     override func mouseDown(with event: NSEvent) {

            Draw.drawCircle(context, center: curves[0].points[3], radius: 3, offset: offset)
            Draw.drawCircle(context, center: B, radius: 3, offset: offset);
        })
        let demo3 = Demo(controlPoints: controlPoints, drawFunction: { (context: CGContext, demo: Demo) in
            let curve = CubicBezier( p0: self.draggables[0].bkLocation,
                                     p1: self.draggables[1].bkLocation,
                                     p2: self.draggables[2].bkLocation,

            Draw.drawSkeleton(context, curve: curve)
            Draw.drawCurve(context, curve: curve)
        })
        let demo2 = Demo(controlPoints: [],
                         drawFunction: { (context: CGContext, demo: Demo) in
            let p1 = BKPoint(x: 110, y: 50)
            let B = BKPoint(x: 50, y: 80)
            let p3 = BKPoint(x:135, y:100)
