What a strange experience.
First of all, I liked the little details like the mouse cursor not showing up outside the monitor or the virtual mouse moving along as I was moving mine. Also, since there were chat windows open most of the time, the changes in the desktop background were nice and subtle.
As for improvements, I think the background music didn't loop fully/you could hear when it started over. Not sure if that's intentional, but if you feel like it, you could maybe make a smoother transition.
The ending gave me goosebumps, which I think is a job well done. It's a short game, but it did what it was supposed to do, although I wouldn't have minded if it was longer.
To me, it had similar vibes to those urban legend horror stories we used to tell each other during sleepovers :)