var e_speed:Number=1;
var ychange:Number;
var xchange:Number;
var myRotation:Number = 0

stage.addEventListener(Event.ENTER_FRAME,enemymove);

function enemymove(e:Event):void {
    myRotation = myRotation + (Math.round(Math.random()*30-15));
    ychange = (Math.cos((Math.PI/180)*myRotation))*e_speed;
    xchange = (Math.sin((Math.PI/180)*myRotation))*e_speed;
    if (x<0) { x = 350; }
    if (x>350) { x = 0; }
    if (y<0) { y = 200; }
    if (y>200) { y = 0; }
    y = y-ychange;
    x = x+xchange;
    rotation = myRotation;
}