dragFlag = false;
dragObj = null;
sy = 100;
document.scroll = function(){
   return {
      y: this.body.scrollTop  || this.documentElement.scrollTop
   };
};
// イベントハンドラなどを設定//  window.onscroll = window.onresize 
Event.observe(window, "load", function(){

	$("video").style.left = (document.body.offsetWidth - 600) + "px";
	$("video").style.top = "100px";
	Event.observe("video", "mousedown", function(e){
		dragFlag = true;
		offsetX = Event.pointerX(e) - parseInt($("video").style.left);
		offsetY = Event.pointerY(e) - parseInt($("video").style.top);
	});

	Event.observe("video", "mouseup", function(){
		dragFlag = false;
	});

	Event.observe("video", "mousemove", function(e){
		var x = Event.pointerX(e);
		var y = Event.pointerY(e);

		if(!dragFlag) return;
		if(Event.isLeftClick(e)){
			if(x - offsetX > document.body.offsetWidth - 320){//右に行き過ぎたとき
				$("video").style.left =(document.body.offsetWidth - 320) + "px";
			}else if(x - offsetX < 0){//左に行き過ぎたとき
				$("video").style.left = "0px";
			}else{
				$("video").style.left = (x - offsetX) +"px";
			}

			if(y - offsetY < 19){//上に行き過ぎたとき
				$("video").style.top = "19px";
			}else{
				$("video").style.top = (y - offsetY) +"px";
			}
			sy = parseInt($("video").style.top) - document.scroll().y;
		}
	});

	window.onscroll = function(){
		$("video").style.top = (sy + document.scroll().y)+ "px"; 
	}
	window.onresize = function(){
		$("video").style.left = (document.body.offsetWidth - 600) + "px";
	}
});