Since the buttons are real models instead of GUI elements, We plan to use Unity's raycasting command to tell which button the user presses. When the user clicks on a button, a related light will be shining and the gear in the middle will be spinning, indicating the door is going to open. (shown as picture 2)
After all of the animations, the door will open and the scene will go through piece of tunnel and reach another door which carries some other buttons. (shown in picture 3)
Although the GUI is also in the tunnel, the position and angle of the camera are different from those in game because we want to focus on the buttons on the door to make it more convenient.
In the next few days we will implement the textures and shaders to the scene and add script to the models for user control.