Flyng pollen (another problem)

programming flash
1

Hi everyone!
I’m using the tutorial to create falling snow for flying pollen but I can’t make the particles move horizontally. They go straight on from the bottom to the top of the stage. It’s not good.

This is the code:
onClipEvent (load) {
//specifies the size of the movie stage
movieWidth = 900;
movieHeight = 600;

//random x,y, and alpha
this._xscale = this._yscale=50+Math.random()*75;
this._alpha = 25+Math.random()*100;

//random x and y for flakes
this._x = -10+Math.random()*movieWidth;
this._y = -10+Math.random()*movieHeight;

//speed and trigonometric value
i = 1+Math.random()*2;
k = -Math.PI+Math.random()*Math.PI;
}

onClipEvent (enterFrame) {
// horizontal movement
rad += (k/180)*Math.PI;
this._x -= Math.cos(rad);
// vertical movement
this._y -= i;

if (this._y<=-5) {
this._y = Stage.height + 5;
}
if ((this._x>=movieWidth) || (this._x<=0)) {
this._x = -10+Math.random()*movieWidth;
this._y = Stage.height + 5;
}
}

Thanks =)