Can get to fade in but no fade out

programming flash
1

Any of you guys know why the following code will fade in but not fade out?

circle._alpha = 0;

function animate():Void {
	circle._alpha++;
	if (circle._alpha>99) {
		reverse();
	}
}
function reverse():Void {
	circle._alpha--;
	if (circle._alpha<1) {
		animate();
	}
}

circle.onEnterFrame = function(){
	animate();
		}

Thanks for your help,
-Nimbusism