Simple radial proximity with AS3

RadialProximity

//demo @ http://adamcoulombe.info/lab/as3/rangetest.swf
//download .fla http://adamcoulombe.info/lab/as3/rangetest.fla
range.visible=false;
stage.addEventListener(Event.ENTER_FRAME,tick);
function tick(e){
	if(getDistance(mouseX,mouseY,source.x,source.y)<range.width/2){
		range.visible=true;
	}else{
		range.visible=false;
	}
}

function getDistance(x1:Number, y1:Number, x2:Number, y2:Number)
{
	var dx:Number = x2 - x1;
	var dy:Number = y2 - y1;
	return Math.sqrt(dx*dx + dy*dy);
}