В первый кадр и тестим

Код:
Stage.scaleMode = "noScale";
Stage.align = "TL";
c = 0;
F_createRandomCube = function () {
_root.createEmptyMovieClip("mc"+c, c);
var m = _root["mc"+c];
var Height = random(10);
var Width = random(10);
m._alpha = random(50)+35;
m._rotation = random(180);
m._x = random(Stage.width);
m._y = random(Stage.height);
with (m) {
beginFill(0x000000);
moveTo(0, 0);
lineTo(0, Height);
lineTo(Width, Height);
lineTo(Width, 0);
lineTo(0, 0);
endFill();
}
m.onEnterFrame = function() {
this._alpha -= 1;
if (this._alpha<=0) {
removeMovieClip(this);
}
};
c++;
};
_root.interval = setInterval(F_createRandomCube, 50);