Okay, so…your computer recognizes the DVD box as an object that it can act upon. And the box becomes a controller for moving the 3D virtual ship, like a mouse or a joystick. But the box also becomes a screen on which information is displayed. A screen within the screen. And you are also on the screen, holding the screen-within-a-screen. However, the DVD box that you — the physical you sitting in front of the computer– are holding isn't actually doing anything. It's just a box. But the box that the "you" on the screen is holding is doing all sorts of magical things. At this point, the illusion that you're looking at yourself is dispelled. It's as if you gazed at yourself in a mirror, and suddenly noticed that your reflection was wearing different socks.