function rand(mi, ma) {
    var range = ma - mi;
    var out = mi + math.round(math.random() * range);
    return parseint(out);
}

function getviewsize() {
    var de = document.documentelement;
    var db = document.body;
    var vieww = de.clientwidth == 0 ? db.clientwidth : de.clientwidth;
    var viewh = de.clientheight == 0 ? db.clientheight : de.clientheight;
    return array(vieww, viewh);
}


$(function(){
	airballoon('div.air-balloon');
});

/*
@function 热气球移动
@update by julying , 2012/7/25
*/
function airballoon(balloon){
	var viewsize = [] , viewwidth = 0 , viewheight = 0 ;
	resize();	
	$(balloon).each(function(){
		$(this).css({top: rand(40, viewheight * 0.5 ) , left : rand( 10 , viewwidth - $(this).width() ) });
		fly(this);
	});	
	$(window).resize(function(){
		resize()
		$(balloon).each(function(){
			$(this).stop().animate({top: rand(40, viewheight * 0.5 ) , left : rand( 10 , viewwidth - $(this).width() ) } ,1000 , function(){
				fly(this);k
			});
		});
	});
	function resize(){
		viewsize = getviewsize();
		viewwidth = $(document).width() ;
		viewheight = viewsize[1] ;
	}
	function fly(obj){
		var $obj = $(obj);
		var currenttop = parseint($obj.css('top'));
		var currentleft = parseint($obj.css('left') );
		var targetleft = rand( 10 , viewwidth - $obj.width() );
		var targettop = rand(40, viewheight /2 );
		/*求两点之间的距离*/
		var removing = math.sqrt( math.pow( targetleft - currentleft , 2 )  + math.pow( targettop - currenttop , 2 ) );		
		/*每秒移动24px ，计算所需要的时间，从而保持 气球的速度恒定*/
		var movetime = removing / 40;		
		$obj.animate({ top : targettop , left : targetleft} , movetime * 1000 , function(){
			settimeout(function(){
				fly(obj);
			}, rand(1000, 3000) );
		});	
	}
};