[a5810]

Some details of the descriptions which i tried to implement: (make it simplest)
* Magnification of a binoculars will be set to 4.0 (fixed). Thus an original view x, when a player has just joined the server, should be got. Then we have the zoom-in view z: z = x / 4.0
* A user presses the use key, and whatever the view, third-person perspective or first-person perspective, will be changed to the first-person perspective with the zoom-in view z (changed in an instant, 0 seconds). Then, when we don’t use it, we press the use key again and it will restore the third-person perspective or first-person perspective.
You can see those problems.