This is hitting the world now in social media in more than just this one video. I tried it, doesn't matter how big the paper is if it lies flat and you can still leave enough mirror showing around the edges to see with. Paper color, size, shape, object dimensions colors, etc are of ZERO influence!
Now I am going nuts thinking over and over "think mirror", and recalling the scenes from the movie Interstellar...

https://youtu.be/TMxJnoPOFkg?si=yfrSdVbG93L3-a-w

And feel like I am stuck inside one of these!

https://youtu.be/hSvR7NXX3ek?si=FADiBl3T-TDWn6rv

When will they kick the lid off this box so we can see out?