cubicCurveTo

package  {

    import flash.display.MovieClip;
    import flash.events.MouseEvent;
    import flash.events.Event;
    import flash.geom.Point;
    import flash.display.Graphics;

    public class Main extends MovieClip
    {

        private var snapSize:int = 10;
        private var points:Array;
        private var halfStageHeight:Number;
        private var halfStageWidth:Number;
        public function Main() {

            halfStageWidth = stage.stageWidth/2;
            halfStageHeight = stage.stageHeight/2
            points = new Array();
            stage.addEventListener(MouseEvent.CLICK, onClick);
            stage.addEventListener(MouseEvent.MOUSE_MOVE, onMouseMove);
            graphics.beginFill(0xFF0000);
            graphics.drawCircle(halfStageWidth, halfStageHeight, 2);
        }
        private function onClick(e:MouseEvent):void
        {
            if(points.length > 1)
            {
                var ax = mouseX;
                var ay = mouseY;
                var bx = points[0].x;
                var by = points[0].y;
                if((bx - snapSize < ax && bx + snapSize > ax) && (by - snapSize < ay && by + snapSize > ay))
                {
                    ax = bx;
                    ay = by;
                    stage.removeEventListener(MouseEvent.CLICK, onClick);
                    stage.removeEventListener(MouseEvent.MOUSE_MOVE, onMouseMove);
                }
                points.push(new Point(ax, ay));
            }
            else
                points.push(new Point(mouseX, mouseY));
        }
        private function onMouseMove(e:MouseEvent):void
        {
            if(points.length > 0)
            {
                graphics.clear();
                graphics.beginFill(0xFF0000);
                graphics.drawCircle(halfStageWidth, halfStageHeight, 2);
                graphics.lineStyle(4, 0xFFFFFF);
                graphics.beginFill(0xFFFFFF);
                graphics.moveTo(points[0].x, points[0].y);
                if(points.length > 1)
                {
                    for(var i:int = 1; i < points.length; i++)
                        graphics.cubicCurveTo(halfStageWidth, halfStageHeight, halfStageWidth, halfStageHeight, points[i].x, points[i].y);

                    var ax = mouseX;
                    var ay = mouseY;
                    var bx = points[0].x;
                    var by = points[0].y;
                    if((bx - snapSize < ax && bx + snapSize > ax) && (by - snapSize < ay && by + snapSize > ay))
                    {
                        ax = bx;
                        ay = by;
                    }
                    graphics.cubicCurveTo(halfStageWidth, halfStageHeight, halfStageWidth, halfStageHeight, ax, ay);
                }else
                    graphics.cubicCurveTo(halfStageWidth, halfStageHeight, halfStageWidth, halfStageHeight, mouseX, mouseY);
            }
        }
    }
}