var NUM_CIRCLES = 3;
var RADIUS = 30;
var curElem = null;

function start(){
	drawCircles();
	mouseDownMethod(mouseDown);
	mouseDragMethod(drag);
	mouseUpMethod(mouseUp);
}

function mouseDown(e){
    var elem = getElementAt(e.getX(), e.getY());
    curElem = elem;
}

function drag(e){
    if(curElem != null){
        curElem.setPosition(e.getX(), e.getY());
    }
}

function mouseUp(e){
    curElem = null;
}

function drawCircles(){
	for (var i = 0; i < NUM_CIRCLES; i++) {
		var circle = new Circle(RADIUS);
		var x = Randomizer.nextInt(RADIUS, getWidth() - RADIUS);
		var y = Randomizer.nextInt(RADIUS, getHeight() - RADIUS);
		circle.setPosition(x, y);
		circle.setColor(Randomizer.nextColor());
		add(circle);
	}
}