It is bound to open to the outside world. Look at the gate. The door built on the mountain is not a real door. There are retractable doors for cars to walk on both sides. The steps hundreds of meters wide in the middle are for people to go in and out. They never close the door, let alone close it, because there is no way. . . You are always welcome to attend the class. You can take any class as long as you want and have a seat. Don't worry! You are not allowed to be with outsiders in the dormitory, but ... yes, as long as there is an empty bed, no problem! Nobody checked, don't worry!