Animate Along a Path

stage.frameRate = 30;
var pencil:Shape = new Shape();
addChild(pencil);

var index:int = 0;
var points:Array = new Array();
var circle:Shape = new Shape();
circle.graphics.beginFill(0x000000);
circle.graphics.drawCircle(0,0, 5);
addChild(circle);

stage.addEventListener(MouseEvent.MOUSE_DOWN, onDown);
stage.addEventListener(MouseEvent.MOUSE_UP, onUp);

circle.addEventListener(Event.ENTER_FRAME, onMoveCircle);

function onDown(evt:MouseEvent):void {
	pencil.graphics.lineStyle(0,0x000000);
	pencil.graphics.moveTo(mouseX, mouseY);
	stage.addEventListener(MouseEvent.MOUSE_MOVE, onDraw);
}

function onUp(evt:MouseEvent):void {
	stage.removeEventListener(MouseEvent.MOUSE_MOVE, onDraw);
}

function onDraw(evt:Event):void {
	pencil.graphics.lineTo(mouseX, mouseY);
	points.push(new Point(mouseX, mouseY));
}

function onMoveCircle(evt:Event):void {
	if (points.length>0) {
		circle.x += (points[index].x - circle.x) / 4;
		circle.y += (points[index].y - circle.y) / 4;
		index++;
		if (index==points.length) {
			index=0;
		}
	}
}

Wrote this in response to a student question. It causes a circle shape to animate along lines drawn by the user.