<script type="text/javascript">
	var lamp={
		red: {
			obj: document.getElementById('red'),
			timeout:30,
			style:['red','gray','gray'],
			next:'green'
		},
		yellow: {
			obj: document.getElementById('yellow'),
			timeout:5,
			style:['gray','yellow','gray'],
			next:'red'
		},
		green: {
			obj: document.getElementById('green'),
			timeout:35,
			style:['gray','grat','green'],
			next:'yellow'
		},
		changeStyle(style){
			this.red.obj.className=style[0];
			this.yellow.obj.className=style[1];
			this.green.obj.className=style[2];
		}
	};

	var count={
		obj: document.getElementById('count'),
		change:function(num){
			this.obj.innerHTML=(num<10)?('0'+num):num;
		}
	};

	var now=lamp.green;
	var timeout=now.timeout;
	lamp.changeStyle(now.style);
	count.change(timeout);

	setInterval(function() {
		if(--timeout<=0){
			now=lamp[now.next];
			timeout=now.timeout;
			lamp.changeStyle(now.style);
		}
		count.change(timeout);
	},1000);
</script>