var maxTop = 100;
var minTop = 80;
var maxLeft = 250;
var minLeft = -350;
var maxSpeed = 1;
var maxElev = 1;
var horDir = 0;
var verDir = 0;
function drift() {
	var z=document.all.pbe001.style;

	function elev() {
		if (verDir==0) {
			z.pixelTop += maxElev;
			if (z.pixelTop == maxTop) verDir=1;
		}
		else {
			z.pixelTop -= maxElev;
			if (z.pixelTop == minTop) verDir=0;
		}
	}

	if (horDir==0) {
		z.pixelLeft += maxSpeed;
		if (z.pixelLeft == maxLeft) horDir=1;
	}
	else {
		z.pixelLeft -= maxSpeed;
		if (z.pixelLeft == minLeft) horDir=0;
	}
	if (z.pixelLeft % 5 == 0) elev();
}