//Programmatic Animation Using ENTER_FRAME Events

var yspeed:Number = -15;
var xspeed:Number = 4;
var gravity:Number = .5;

ball_mc.addEventListener(Event.ENTER_FRAME, onFrameLoop);
function onFrameLoop(e:Event) {

yspeed += gravity;
ball_mc.y += yspeed;
ball_mc.x += xspeed;

if (ball_mc.y > stage.stageHeight) {

//uncomment below to return to top of stage
//ball_mc.y = - ball_mc.height;

//reverse speed to bounce
yspeed = - yspeed;

}

if (ball_mc.x > stage.stageWidth || ball_mc.x < 0) {
xspeed = -xspeed;
}

}