var startTime=new Date();
var endTime=new Date();
var startPressed=false;
var bgChangeStarted=false;
var maxWait=20;
var timerID;

function startTest() {
	document.bgColor=document.response.bgColorChange.options[document.response.bgColorChange.selectedIndex].text;
		bgChangeStarted=true;
		startTime=new Date();
}

function remark(responseTime) {
	var responseString="";
		if (responseTime < 0.10) responseString="Well done!";
		if (responseTime >= 0.10 && responseTime < 0.20) responseString="Nice!";
		if (responseTime >=0.20 && responseTime < 0.30) responseString="Could be better...";
		if (responseTime >=0.30 && responseTime < 0.60) responseString="Keep practicing!";
		if (responseTime >=0.60 && responseTime < 1) responseString="Have you been drinking?";
		if (responseTime >=1) responseString="Did you fall asleep?";
			return responseString;
}

function stopTest() {
	if(bgChangeStarted) {
		endTime=new Date();
		var responseTime=(endTime.getTime()-startTime.getTime())/1000;
		document.bgColor="white";       
		alert("Your response time is: " + responseTime + " seconds " + "\n" + remark(responseTime));
		startPressed=false;
		bgChangeStarted=false;
	}
		else {
			if (!startPressed) {
				alert("press start first to start test");
			}
		else {       
			clearTimeout(timerID);
			startPressed=false;             
			alert("cheater! you pressed too early!");
		}               
	}
}

var randMULTIPLIER=0x015a4e35;
var randINCREMENT=1;
var today=new Date();
var randSeed=today.getSeconds();

function randNumber() {
	randSeed = (randMULTIPLIER * randSeed + randINCREMENT) % (1 << 31);
	return((randSeed >> 15) & 0x7fff) / 32767;
}

function startit() {
	if(startPressed) {
		alert("Already started. Press stop to stop");
		return;
	}
	else {
		startPressed=true; 
		timerID=setTimeout('startTest()', 6000*randNumber());
	}
}