// set gravity amount
var gravity:Number = .00098;

// set starting velocity
var dx:Number = .05;
var dy:Number = -.9;

// mark start time and add listener
var lastTime:int = getTimer();
addEventListener(Event.ENTER_FRAME, animateBall);

// step animation
function animateBall(event:Event) {
	var b2:ballSymbol;
	
	// get time difference
	var timeDiff:int = getTimer() - lastTime;
	lastTime += timeDiff;
	
	// adjust vertical speed for gravity
	dy += gravity * timeDiff;

    // move ball
	ball.x += timeDiff * dx;
	ball.y += timeDiff * dy;

    b2 = new ballSymbol();
	b2.x = ball.x;
	b2.y = ball.y;
	b2.alpha = 0.4;
    
	
    addChild(b2);
	
    if (ball.y + dy >= 400 && dy > 0)   // bouncing ball
	{
		dy = 0.95 * dy;         // reduce height of bounce
		dy = -dy;
		// dx = 0.97 * dx;
	}
}