//Import TweenMax
import gs.*;
 
/* Vanishing point for the y coordinate. So when the object is really far away, the y coordinate is almost equal to the vanishing point. */
var vanishingPointY:Number = stage.stageHeight / 2;
 
//Focal length determines how much perspective is seen.
var focalLength:Number = 300;
 
//This array will hold all our circles and the text
var itemsArray:Array = new Array();
 
//Add our text to the array
itemsArray.push(myText);
 
//Add our circle to the array
itemsArray.push(myCircle);
 
//Angle speed for the circle
var angleSpeed:Number = 0.2;
 
//Horizontal speed for the circle
var xSpeed:Number = 4;
 
//The y radius (height) of our "tunnel" is determined by the text height
var yRadius:Number = myText.height;
 
//The z radius (depth) is calculated from the yRadius
var zRadius:Number = yRadius * 3;
 
//Assign an initial 3D y and z coordinate
myCircle.ypos3D = 0;
myCircle.zpos3D = 0;
 
//Assign a 3D z position for the text so we can animate the circle around it
myText.zpos3D = 0;
 
//Initial angle for the circle
myCircle.currentAngle = 0;
 
//Add an ENTER_FRAME listener so we can animate the circle
myCircle.addEventListener(Event.ENTER_FRAME, moveCircle);
 
/* We start a timer at the beginning of the movie. In each timer event, we will create a new trail circle. */
var timer:Timer = new Timer(20,0);
timer.addEventListener(TimerEvent.TIMER, createTrail);
timer.start();
 
//This function moves the circle ("myCircle" instance)
function moveCircle(e:Event):void {
 
        //Update the circle's angle
        myCircle.currentAngle += angleSpeed;
 
        //Calculate the new 3D y position
        myCircle.ypos3D=Math.sin(myCircle.currentAngle)*yRadius;
 
        //Calculate the new 3D z position
        myCircle.zpos3D=Math.cos(myCircle.currentAngle)*zRadius;
 
        //Calculate a scale ratio
        var scaleRatio = focalLength/(focalLength + myCircle.zpos3D);
 
        //Scale the circle according to the ratio
        myCircle.scaleX=myCircle.scaleY=scaleRatio;
 
        //Update the x coordinate
        myCircle.x+=xSpeed;
 
        //Update the y coordinate
        myCircle.y=vanishingPointY+myCircle.ypos3D*scaleRatio;
 
        //If the circle is over the right side, move it to the left
        if (myCircle.x>stage.stageWidth+20) {
                myCircle.x=-20;
        }
 
        //Call the function that sorts the circles so they overlap correctly
        sortZ();
}
 
//This function creates a new trail circle
function createTrail(e:Event):void {
 
        //Create a new circle
        var newCircle:MyCircle = new MyCircle();
 
        //Assign the same z position as the "myCircle" has
        newCircle.zpos3D=myCircle.zpos3D;
 
        //Assign the same coordinates
        newCircle.x=myCircle.x;
        newCircle.y=myCircle.y;
 
        //Calculate the scale ratio
        var scaleRatio = focalLength/(focalLength + newCircle.zpos3D);
 
        //Scale the circle according to the ratio
        newCircle.scaleX=newCircle.scaleY=scaleRatio;
 
        //Push the circle to the the items array
        itemsArray.push(newCircle);
 
        //Add the circle to the stage
        addChild(newCircle);
 
        //Call the sorting so the new circle overlaps correctly
        sortZ();
 
        /* Use TweenMax to scale down the circle. We call the function removeCircle when the tween is finished. */
        TweenMax.to(newCircle, 2, {alpha: 0, scaleX:0, scaleY:0, onComplete: removeCircle, onCompleteParams: [newCircle]});
}
 
//This function is called when a circle tween is finished
function removeCircle(circle:MyCircle):void {
 
        //Remove the circle from the array
        var i:uint=itemsArray.indexOf(circle);
        itemsArray.splice(i, 1);
 
        //Remove the circle from the stage
        removeChild(circle);
}
 
//This function sorts the circles so they overlap each others correctly
function sortZ():void {
 
        /* Sort the array so that the circle which has the highest z position (= furthest away) is first in the array. */
        itemsArray.sortOn("zpos3D", Array.NUMERIC | Array.DESCENDING);
 
        //Set new child indexes for the items
        for (var i:uint = 0; i < itemsArray.length; i++) {
                setChildIndex(itemsArray[i], i);
        }
}