var container = $(".coins");
var lastTime = new Date().getTime();
var count = 0;
var hand = $(".hand");

function loop(){
  // 控制时间间隔  保证1秒最多60帧
  var now = new Date().getTime();
  if(now - lastTime < 17){
  	requestAnimationFrame(loop);
    return;
  }
  lastTime = now;
  
  // 执行正常每一帧的逻辑
  if(count-- == 0){
    var coin = $("<div class='coin'>")
  	coin.css({left:Math.random()*500, top:0});
  	container.append(coin);
    count = 30;
  }
  
  
  container.children().each(function(){
    $(this).css({ top: parseInt($(this).css("top"))+5 });
    if(parseInt($(this).css("top")) > 500){
      var offsetX = parseInt($(this).css("left")) - parseInt(hand.css("left"));
      debugger;
      if(offsetX>50 || offsetX<-50){
        $(this).css({background:"#999999"});
      }else{
        $(this).remove();
      }
     
    }
  });

  // 播放下一帧动画
  requestAnimationFrame(loop);
}

loop();

$(document).on("mousemove", function(e){
  hand.css({left : e.clientX});
});