responsive design con adapt.js

test.html

<script>
	// Responsive design with adapt.js
	function resize_callback(i, width) {
		if (i > -1) {
			if (i == 0)
				$("body").removeClass().addClass("mobile");
			else if (i == 1)
				$("body").removeClass().addClass("tablet");
			else if (i == 2 || i == 3)
				$("body").removeClass().addClass("regular");
		}
	}

	var ADAPT_CONFIG = {
		path: 'css/',
		callback: resize_callback,
		dynamic: true,
		range: [
			'0px    to 760px  = mobile.css',
			'760px  to 980px  = 720.css',
			'980px  to 1920px = 960.css',
			'1920px = 960.css'
		]
	};
</script>
<script src="js/adapt.min.js"></script>