code: function(group,key){
  		var bd = this.board;
  		var margin = bd.initGroup(group, bd.cols, bd.rows);
  		var groups = bd.getGroup(group);
  		var groups2 = new groups.constructor();
  		bd.setposGroup(group);
  		for(var i=groups.length-1;i>=0;i--){
  			var piece = groups[i];
  			if(this.isdel(key,piece)){
  				piece = bd.newObject(group, i);
  				groups[i] = piece;
  				groups2.add(piece);
  				margin--;
  			}
  			else if(margin>0){ groups[i] = groups[i-margin];}
  		}
  		groups2.allclear(false);
  
  		if(group==='border'){ this.expandborder(key);}
  	}
docs: ------------------------------------------------------------------------------ bd.exec.expandGroup()  オブジェクトの追加を行う bd.exec.reduceGroup()  オブジェクトの消去を行う bd.exec.isdel()        消去されるオブジェクトかどうか判定する ------------------------------------------------------------------------------