$(function() {
	var before = null;
	var x = 400;
	var STEP = 5;
	var bouge = function(div, delta){
		x += delta;
		if(x > 1200) {
			x -= 1200;
		}
		if(x < 0) {
			x += 1200;
		}
		div.css("background-position", x + 'px 0');
	};
	$("div#top")
		.bind('mousewheel', function(evt, delta) {
			bouge($(this), delta * STEP);
			return false;
		})
		.mousemove(function(evt) {
			if(before != null) {
				if(before > evt.clientX) {
					bouge($(this), STEP);
				} else {
					bouge($(this), -STEP);
				}
			}
			before = evt.clientX;
		});
});