Snow falling

1

Well, now is winter time and we are all starting to make our logos with snow. I have this code for snow, but there is a problem.


var swidth = 250;
var sheight = 200;
_root.createEmptyMovieClip("DropClip", 15999);
for(var i=0; i<80; i++)
{
	createdrop(random(sheight));
}
var lightstorm = setInterval(createdrop, 30);
function createdrop(y)
{
	var clip = "drop" + Math.random();
	_root.DropClip.attachMovie("Drop", clip, random(15999));
	_root.DropClip[clip]._x = random(400);
	if(y != null)
	{
		_root.DropClip[clip]._y = y;
	}
		
	_root.DropClip[clip]._alpha = random(100);
	_root.DropClip[clip].speed = random(4);
	_root.DropClip[clip].onEnterFrame = fall;
}

function fall()
{
	if(this._y < sheight)
	{
		this._y += 1 + this.speed;
	}
	else
	{
		delete this.onEnterFrame;
		this.removeMovieClip();
	}
}

Now, my animation is 250x200 pixels. Where do I have and what do I have to insert that my snow start fall 20 pixels from 0 y and x wide.

I have 20 pixels black border on my animation, bu snow is falling on that border, too. I wont wont that. I wont that snow fall only in my picture.

Thanks.