function s_chg(td_now)
{
	if(td_now.id == "Pop_Music")
	{
		Pop_Music.className="zy1";
		Folk_Music.className="zy2";
		Hot_Film.className="zy2";
		Lecture_Room.className="zy2";
		shield1.className="link5";
		shield2.className="link6";
		shield3.className="link6";
		shield4.className="link6";
		
	}
	if(td_now.id == "Folk_Music")
	{
		Pop_Music.className="zy2";
		Folk_Music.className="zy1";
		Hot_Film.className="zy2";
		Lecture_Room.className="zy2";
		
		shield1.className="link6";
		shield2.className="link5";
		shield3.className="link6";
		shield4.className="link6";
		
	}
	if(td_now.id == "Hot_Film")
	{
		Pop_Music.className="zy2";
		Folk_Music.className="zy2";
		Hot_Film.className="zy1";
		Lecture_Room.className="zy2";
		
		shield1.className="link6";
		shield2.className="link6";
		shield3.className="link5";
		shield4.className="link6";
	}
	if(td_now.id == "Lecture_Room")
	{
		Pop_Music.className="zy2";
		Folk_Music.className="zy2";
		Hot_Film.className="zy2";
		Lecture_Room.className="zy1";
		
		shield1.className="link6";
		shield2.className="link6";
		shield3.className="link6";
		shield4.className="link5";
		
	}
	}