//背景图移动,营造船在前进的视觉效果
背景设置repeat-y;
.page3_bg{
position:relative;width:100%;height:100%;
background:url(../image/page3_bg.png) repeat-y;
background-size:100% 603px;
background-position:0 0px;-webkit-transition:all 0.5s linear;
}
var nowY=$("#gamePage").css("background-position-y");
var newY=parseInt(nowY)+self.steps*self.stepsView;
$("#gamePage").css("background-position-y",newY+'px');